But there is one for Linux distributions, released more than a year ago as binary only (not sources at the moment) called "Spine" (like as Wine Spine is not an emulator) that's pretty real and can run a few/couple of commercial titles.

Yeah, more a POC that a full emulator but I can assure you that it works, assuming you can decrypt the supported titles, so you'll need an exploitable PS4 or find a dump on the Interweb...

Edit: link https://github.com/devofspine/spinedemo