Sorcery and Super Science might work for this. It’s already most of the way there. Most characters are mutants though and all humans are sorcerers so it might not be a perfect fit

You can also try a bit of a combo move with Worlds Without Number and Stars Without Number. Both games could probably handle this by themselves, but the rules are similar enough to combine which would give you scifi and magic together

If you don’t mind a little bit of legwork, 2400 should work pretty well. You can find it on DrivethruRPG. The rules are pretty straightforward and the setting does most of the heavy lifting for you