Ugh, an upgrade broke my home server. To make it even more enjoyable, the screen backlight of the old Thinkpad it's installed on died, and my desktop monitor doesn't have a VGA input.
I managed to boot on a live disk and setup SSH by sticking a flashlight on the screen, and am now dding the 1TB disk to an external hard drive in order to chroot into it, fix the issue if possible and dd it back.
That's what I get for not using iCloud I guess 🤷