You could install linux-lts, I sometimes use that as a sanity check in case there is some kernel fuckery

Did you also update systemd at the same time? It might be worth reverting that update to see whether it’s that causing the issues.

To me, this sounds more like an fstab/systemd-automount issue rather than a bootloader/initrd issue

ArchWiki is your friend

Any particular reason you’re not on/tested the v590-branch? Of course it might be borked compared to 570, but might be worth a shot?