I'm having the same problem as poltergeist, tried downloading the ppsspp 1.3 but its exactly the same, i need help xD
EDIT: never mind, turns out the latest nightly build got vulkan compatibility and it works even better with that xD
Not sure about other models of Pi4 but the Pi 4 B with 8GBs OCed to 2Ghz handles PSP really great except like 1 game I found and it is playable it just looks bad lol Motor Storm Arctic something or other.