Not sure if it's desired or the right place for it, but here is some feedback based on my gameplay. Although I don't think it matters much for most of this, my settings were Survivalist, Horde Every Night, 24 zombies BM spawn cap, 120 Min days (weak I know, but I like to have a little breathing room with horde every night), and Jog during the day, other settings at default. So far on Day 19, lvl 75 with 5863 kills. Also I play with self imposed rules of 'no cheesing/running away from the horde', I have to kill every horde and I can't use a defence that they can't meaningfully damage/get at me somehow. Started off with STR/INT for mining/crafting with no combat skills, then later on picked up AGI for Handguns as my main combat skill, with a side of explosives/shotguns for fun/situational use. Kept notes on overall progression (ie when I got vehicles, certain key items), but I don't think it's relevant here.
Loot Progression
While overall I feel like the loot progression is more or less fine (maybe could use more tweaks), there are a few rough patches that might need to be looked at. One of the issues is that the way loot transitions between 'tiers' is you go from getting Q5-6 items of a previous tier into Q1-2 items of the next tier. Sometimes this is fine, but in many cases a lower tier Q5-6 item is just straight up way better then a Q1-2 of the next tier. For example a Q5-6 AK is going to be way better then a Q1-2 Tac Rifle, since the Tac Rifle isn't really much better even at equal quality levels. Marksman to Sniper Rifle is also fairly bad, as the damage is basically the same and the only real advantage of the Sniper is it has a bigger magazine size. This is especially bad with stone to iron tools, as Q5-6 stone tools use little stamina and are superior to really bad iron tools. It's the worst with shovels, due to basically every diggable thing being 200 or 250 HP and this means in most cases the way the breakpoints play out, if you have points in mining a high quality Stone Shovel will usually dig as fast as a medium quality Iron Shovel. If you don't have points in mining to make the breakpoints more favourable, then you probably also don't have points in stamina since it's also under STR, so the Iron Shovel will be slower then the Stone due to stamina problems. However, this honestly is a problem with almost every item class. There are only rare cases I would use a Q1-2 item of a 'higher tier' then a Q5-6 of the previous, which would basically be Auger/Chainsaw over Steel Tools, and Marksman Rifle over Hunting Rifle (because the Hunting Rifle is just terrible), and probably a few others I'm forgetting.
Speaking of stone tools, if you are going to extend the stone age, adding a stone pickaxe would make sense, as trying to mine iron with a stone axe is like pulling teeth. It would probably help with all the complaining about stamina too, as people wouldn't feel 'forced' to use iron pickaxes before getting a few ranks in Sexual Tyrannosaurus. I got around this by just rushing mining/stamina perks and spamming drinks/coffee and crafting an iron pick, but I could see how it might be frustrating to some if you don't know how to make this transition.
Another problem with these loot tier transitions, is that back in A17 experimental, I remember how sell prices of items were re-balanced such that Q1 items were basically worthless, because in A17 you would get dozens of Q1 guns all the time from loot and it flooded the economy from day 1. However this doesn't make much sense anymore, because now you have situations where you are going from getting Q5-6 Pistols for example, that sell for a lot, to getting Q1-2 Magnums which basically sell for nothing. This obviously isn't game breaking or anything, but it feels pretty bad that often times 'going up' a tier means you actually get worse loot (both in terms of usefulness and sell value) for a while until the quality levels catch up.
While this might not be a serious issue, and there may be other possible solutions I would suggest compressing quality based sell modifiers a little more; ie make Q6 sell for less then currently and Q1 sell for more, as the old issue of getting dozens of Q1 guns on day 1 is no longer the case due to the gated loot. Also making the highest tier items sell for slightly less would probably help the late game economy a little.
Loot Gating
While I already mentioned I generally feel the overall loot progression is fine, I have heard talk of gating things even more, and I would like to voice my concerns about it. Even during my playthrough I honestly seriously considered just stopping looting once I had the absolute basics and just waiting until I leveled up to loot more, as getting more random stone tools/blunderbusses wasn't particularly useful to me. The reason I kept looting was the chance for good mods/schematics/ammo. If more of these 'misc' items were to be tied to gamestage in loot, then I probably wouldn't have bothered to loot more then a few houses for the bare minimums like a Wrench until I was lvl 15-20+. I could see a few top tier schematics being partly level gated, but I don't think the majority should have level gates (and even the high end ones should only have low gates just to avoid them dropping on day 3 or whatever).
Also this is only vaguely related, but while I do think gun ammo should keep dropping even at low levels, there probably is a little bit too much of it. Magnum ammo is still very rare, but 7.62 and 9mm are absurdly common and you can easily get stacks and stacks of them just from loot, esp if you get the magazine for 'more ammo from loot'. Probably could use a tweak.
Difficulty
Now that Gamestage isn't modified by difficulty level, the hordes/sleepers feel pretty weak compared to what I was used to at the same point in progression. I realise this was probably changed to avoid difficulty level affecting loot quality, and it could be argued difficulty scaled gamestage a bit too much before, but I think there is a middle ground to be found here. But I assume this is something, that if it were to be changed back, would be in A20 as it would probably require adding a different GS calculation for hordes/sleepers then for loot.
Weapons/Gunplay
There seems to be this weird jitter/delayed recoil after firing guns now. First you shoot, and you get the recoil. Then about 0.1-0.2 seconds later you get this jitter/jerk, usually back towards the original position as if your character is trying to compensate for recoil. The first time I shot guns in this alpha I thought my hand had a tremor or my mouse was broken, it was pretty strange. Not sure if this is intended functionality, but it doesn't really feel right (the initial recoil is fine, just talking about the 'after jitter').
Zombie Armour/Armour Piercing seems to be broken. When testing hollow point ammo vs AP ammo, HP ammo always did more damage, even vs armoured zombies like Soldiers or Demolishers. What is even more interesting is that Demolishers do still take greatly reduced damage, but they don't seem to care about the ammo's armour modifiers at all; HP ammo does more damage vs them then AP ammo (since HP ammo does more damage by default). So it does seem like armour exists, but ammo isn't interacting properly with it. Penetrator seems to suffer from the same issue (it makes no difference to have it or not vs armoured zombies). Ultimately this means there is little drawback to always using HP ammo (except for Sniper Rifles, which penetrate up to 5 targets with AP ammo making them insane for blood moon hordes).
In terms of general weapon balance, I already touched on some of this, but it's a bit of a mixed bag. The Tac Rifle feels like an AK with a burst mod built in, which is not really all that useful since it's easy to just practice some trigger discipline and go for headshots instead of spraying full auto. It doesn't really feel like a higher tier weapon. Sniper Rifle vs Marksman Rifle is basically an extra extended Mag upgrade, which is nice, but again doesn't really feel like 'higher tier'. Probably the only new weapons that actually feel like a real upgrade over the previous tier is the Desert Vulture over the Magnum, due to higher fire rate, bigger magazine, and way faster reload, which makes it way better despite it's slightly lower damage per shot, and the Combat Shotgun over Pump due to bigger magazine/faster fire rate.
Int weapons in general badly need some love, although I assume it probably won't happen until A20 since it would require adding more weapon types. Stun Batons are just bad, and really need higher/lower tier versions to compete with other melee weapons. The Sledge Turret is serviceable after the buffs, but idk if it's really 'good' still or worth investing in. And the Junk Turret, while stronger then before due to the new ammo types, still has the issue of constantly setting off Demolishers in late game hordes, so you basically can't use it when demos show up, which kinda makes it way too situational. Not sure what the solution is there, because making Junk Turrets NEVER set off Demos would probably be too OP, but as it is you are just playing with fire using them during a late game horde, and it makes it feel even worse to invest into INT weapons, because they basically suck early game due to not being available/the sledge turret being iffy, and then they suck in the late game because of this.
I really like what was done with knives/bows with the sneak damage modifier. At least means crossbows aren't strictly worse then guns in all situations anymore, although still situational.
I think this has been mentioned, but the Sniper Rifle first person model needs to be a bit smaller, and it's iron sights/reflex sight need to be improved as they are basically detrimental to you. I know it's intended to be used with a scope, but it could be improved.
I like how Handguns are sticking to the theme of 'resource efficient' with cheaper ammo/good damage per cost ratios combined with high accuracy even in hip fire. Good way to make them distinct. Although I'm not sure the SMG belongs in T3 with the Desert Vulture, as the Vulture is pretty powerful, while the SMG is just a Pistol with a better fire rate and a bigger mag. But to be fair, I don't think Handguns are in any way 'weak', they might actually be the best overall gun type tbh.
Demolishers
It seems a bit odd you can 'trigger' the detonator on a dead Demo (it's purely visual, but if the corpse can't detonate it probably shouldn't be able to visually be primed either). And sometimes when shooting a Demo corpse and removing a limb from it, they will emit a grunt as if they were still alive.
Performance
Not sure what is causing this, but when I am indoors, my GPU is underutilized (1080TI, but I'm not sure the type of card matters tbh) like crazy. The game has no issue using 100% of the GPU outdoors, but when I am indoors (like inside a POI, or inside a horde base), it starts dropping GPU usage over time, down to in some cases 10-30% which causes framerates of 15-20 which is basically unplayable (and it's not some kind of heat throttling, because the card cools down to 50-60C when this happens, it's basically going idle). Usually going outside seems to partly fix the issue, but it's very inconsistent. Sadly I don't really have much more useful information on this and there could be many causes. I just haven't seen anything like this in other games however.
Animals
I'm sure it's already been said, but yeah there are way too many animals since the most recent experimental. Food was already a total non issue even on day 1 before, but now it's completely silly. Too many predators as well, if this many animals are going to spawn, predators should probably be at least partly linked to gamestage (so that there are less of them at lvl 1) to make the game more beginner friendly.
Non A19 Specific Misc Stuff
I don't think this is A19 specific, but I don't like how you get less EXP per block mined with higher tier tools (ie Steel Pick gives less exp then Iron Pick for the same block, and Auger gives less then the Steel pick). While I understand it's likely to curb crazy power leveling via mining (like it was in A16), it's probably too far in the direction of making mining exp almost irrelevant in the late game. Most other sources of EXP naturally scale; higher tier zombies give more exp and you generally kill faster with better weapons, loot exp directly scales with level, and construction exp scales because you tend to build bigger/gather resources faster in the late game. Mining exp feels almost static due to this exp reduction mechanic, and while I was noticing meaningful exp gains from mining in the early game, my exp bar would barely even move later in the game, even speed mining with an auger. Obviously part of that is it just takes more exp to level at higher levels, but I was still levelling almost as fast from looting/killing due to just getting more exp from that for the before mentioned reasons.
This also isn't new, but the Auger and Chainsaw are I think literally the only items still using the old durability system, where their damage goes down as durability goes below 50%. I think all other guns/tools/armour have been changed to work the same at 100% to 1% since multiple alphas ago. Should probably be changed for consistency.
Anyways, there is a lot more to say, esp about perk tree balance, but I think this is enough misc ramblings for one post.