@petsam I somehow fixed it.
Update: You only need to change to another TTY (Ctrl+Alt+F4, you can replace F4 with any function key besides F1 and F2) and remove the EndeavourOS SDDM configs.
sudo pacman -R eos-plasma-sddm-config
If you don’t want to remove that package, follow the instructions here: I'm running Plasma with sddm. After updating I can't login - #20 by Viera
If that doesn't work
Remove SDDM and configs:sudo pacman -R sddm sddm-kcm eos-plasma-sddm-config
Reinstall SDDM (not the configs):
sudo pacman -S sddm sddm-kcm
Re-enable SDDM and reboot
sudo systemctl enable sddm
SDDM will revert to its default LXQt-style look if you remove the package, but it actually works now.
So it was SDDM. I was right 