If you care about RetroAchievement support, this is what they support.
Beetle is the RetroArch core that’s most often recommended. If you don’t like RA (they have serious issues of their own), the Beetle core comes from the emulator Mednafen.
And the other main open-source option is PCSXR.
zarkanian@sh.itjust.works 8 months ago
Mednafen is pretty great.
MAME also has PSX emulation. It’s marked as not working, but I’ve heard it’s actually pretty good, and I got good results on the few games I tried.