Modderitis Fatalis.
The game tries to access Data/Bundles/Other/Items in the game directory which was still in the game as of A19 , but not anymore in A21. Which suggests that at least one mod was not updated for A21.
And then there is a NullReferenceException in the routine CustomModManager.UI.XUiC_ModsErrorMessageBoxWindowGroup.ShowMessageBox which makes the game simply close again.
And some patches from the mods can't get applied which suggests incompatibilites between mods.