Even though the psp is 15 years old retroarch still puts out new releases for it. Unfortunately, a lot of the emulator cores that are included don't work and some even crash the psp. It would be nice to be able to just have retroarch for emulation but installing standalone emulators is pretty much necessary.
Even still, the PSP is a dang powerhouse of retro gaming handheld! Emulators for just about everything from N64/PS1 on back. Quite a bit of homebrew apps and games and plugins for adding features and tweaks. My Odroid Go Advance is pretty neat but I actually kind of prefer my trusty PSP for most things. N64 is the only thing the OGA does better than PSP and the OGA does PSP games worse.