So, I did something really dumb and you’re free to bash me for doing that, but well, here we are:
I had EOS installed alongside my Ubuntu system but decided to remove it for a while because I wanted the disk space back and wasn’t using it daily anymore, so I wipped the root partition and extended my Ubuntu partition over it as usual and to get rid of the boot entry I went into /boot/efi inside my Ubuntu install and deleted the Arch folder inside of it which was probably created by Grub when running OS-prober (OS-prober was ran by Ubuntu because I wanted the Ubuntu grub to dominate the boot).
Now this was really dumb, and as a consequence I cannot boot with the EOS ISO anymore, or even from the base Arch ISO since it seems the ISO wants to find the old boot entry and can’t find it, so it just panics and kicks me back to the boot menu. Other ISO’s work.
The ISO actually boots, now that I tried again, but hangs for 30s before the graphical environment and complains that it can’t find a tty, so it falls back to a rootfs environment. The base Arch ISO gives me an error and reboots, but it’s so fast that I can’t read what the error is (I mention the Arch ISO because I thought the issue was with the missing boot entry).