Regarding, mkinitcpio error message, with hook kms and kernel 5.10, it seems, at this time, to be reporting an error when it probably should be a warning. Testing, if I remove kms from the mkinitcpio.conf HOOKS, the error message does not appear. I captured the verbose output of mkinitcpio, but nothing jumps out as what might be missing. At this time, I’m just ignoring the error message on kernel 5.10.
This archlinux entry, "SOLVED: mkinitcpio exits with code 1 after upgrade from 36 to 37", describes the issue and points to bug report.
Kernel 5.10 doesn’t EOL until 12/2026.
The issue was probably introduced with the upgrade of mkinitcpio to 37 on the 2023-11-21 Stable Update.