This is not the case.
Have you found a "working" file? Join the discussion on r/PSP or GBAtemp—but bring proof, because after 15 years, the community has yet to see a real one.
For years, dedicated coders in the PSP homebrew scene (like the legendary developer V12-Tweak ) attempted to reverse-engineer San Andreas . They managed to get a very, very basic map viewer running. You could walk around a glitchy, textureless Los Santos at 5 frames per second. These are tech demos, not playable games. There is no functional homebrew Eboot PBP of GTA San Andreas.
You can now play GTA 2 on your PSP. It looks decent, but it is not San Andreas .
Inexperienced users often see these files available online and assume they will work on the PSP as well. However, the PSP lacks the raw processing power and RAM required to emulate the PlayStation 2 version of San Andreas natively. The PS Vita has significantly stronger hardware, allowing it to run that Eboot via built-in PS1/PS2 emulation capabilities. If you try to transfer a PS Vita San Andreas Eboot to