Usually that means there is an error booting (or booting using a specific kernel)
If I had to take a guess it might be because DKMS packages, but you can never be sure. Check this FAQ Computer doesn’t boot, boots to a black screen, or stops at a message
If that doesn’t help, try a kernel you know that works (for instance the Zen one; which it should still default to). If that still doesn’t work, you can select a snapshot from a time the system was working Restoring snapshots to get the system back to working state | Garuda Linux wiki (after you follow that guide completely and do your reboot for it, made sure to update your system again with garuda-update )
Is the monitor still reporting as unknown after the reboots?
Do you know the specific make of the monitor and how your are connecting to it (like what cable type)?