Well you can always force a MBR boot. Bot if multi-booting ALL OS must boot the same why or they won’t see each other.
Then again a little Googling will find lots of info such as here from official openSUSE
https://en.opensuse.org/openSUSE:UEFI
Probably more then you really need to know but it covers most of the basics.
Ignorance is bliss but it is also expensive 