Standalone (not retro arch). Modern emulator (don’t think it’s updated anymore though). Linux support. I think it’s also available on Flathub if you want to get it via there.
Multi system emulator originally developed by Near (rip). Yes, it plays more systems than you are looking for, but it is simple, standalone (no retroarch/libretro), very good, Linux support, and still updated (latest version 23 Jan). Also available on Flathub if you want it there.
I suggest to try these emulators, they’re modern and they aim for cycle accuracy, rather than finding a way to keep a 15 year old emulator running.