To be clear, Forza Horizon 5 is not available on PPSSPP. PPSSPP is an emulator for the PlayStation Portable (PSP). Since Forza Horizon 5 was released in 2021 for Xbox and PC, it is technically impossible for a PSP emulator to run it. Any "ISO download" you find online claiming to be FH5 for PPSSPP is almost certainly a modded version of a different game (like Gran Turismo or Need for Speed) or, more dangerously, malware.
PPSSPP is an open-source emulator that enables you to play PSP (PlayStation Portable) games on various devices, including Android smartphones and tablets. Its compatibility with a wide range of PSP games and user-friendly interface makes it a popular choice among gamers. forza horizon 5 ppsspp iso download android mobile install
Since you have PPSSPP installed, why not use it for actual PSP racing games? They won’t be Forza Horizon 5, but many are excellent: To be clear, Forza Horizon 5 is not available on PPSSPP
