is a high-end PlayStation 4 and PC title, it is technically impossible for the PSP hardware (or its emulator) to run it. Fake Files

This is the absolute closest you will get to Days Gone on PSP. It is a third-person shooter set in a post-apocalyptic Europe overrun by mutated creatures (Chimeran Cloven). The gritty atmosphere, ruined cities, and desperate survival tone match Days Gone perfectly.

Sony has started porting some PS4 games to mobile (via cloud streaming or native ports like Resident Evil Village on iPhone 15 Pro). However, there is no official announcement regarding Days Gone for Android.

: Days Gone (2019) is a PlayStation 4 (PS4) and PC exclusive title. It was not developed for the PlayStation Portable (PSP), which is the platform supported by the PPSSPP emulator. Thus, attempting to run Days Gone via PPSSPP is technically impossible due to architectural differences and lack of appropriate ROMs.