Found the problem. My BIOS tried to boot in UEFI mode but it should have been AHCI. No clue why this changed during the upgrade, but glad it's no serious damage.
I messed up my Proxmox 8 to 9 upgrade and now my server won't boot at all. The bios doesn't detect a bootable drive and reboots into the bios settings. Let me explain my f#ckup. I was upgrading from within the Proxmox web UI Shell (yes, dumb). Of...