PS4 and PS5 emulators I don’t think any of them actually emulate the CPU at least. This is more like QEMU and WINE, sort of. They do emulate some stuff like parts of the firmware, memory management, input/output systems, API.

The first PS4 emulator that got in-game with a few 2D titles was literally just a modified version of QEMU as a proof of concept. Only ran on Unix based operating systems because the PS4 runs a modified version of FreeBSD.