After a lot of work, I am very happy to share this with all of you.
Currently it only supports "IR JIT" (which is basically a more optimized Interpreter) and "Interpreter", proper JIT (dynarec) support is still in the works.
Audio & Video support works, many core options cause Issues tho.
It is mandatory to "Close Content" after changing any Core option and restarting RetroArch, else it will potentially crash.
Special thanks to hrydgard for everything he has done for the PPSSPP Project.
If you want to support his work, consider buying PPSSPP Gold https://central.ppsspp.org/buygold even if you don't use it!
I will PR it once the libretro port is finished, also implemented half of what's needed for a Standalone port ;)
Source is on my Github, but it's highly WIP and needs a custom RA and a custom ffmpeg, so you should just wait if you want to build it yourself ;)
Drag & Drop the "retroarch" folder to the root of your SD, overwriting any file (it will not touch any options).
Assets are bundled, so you don't have to bother with that.
If you are using ANY method of loading RetroArch OTHER than Atmosphere's title redirection feature, DO NOT report issues that you encounter.
These issues can skew testing and could very well be caused by loading through an unsupported method.
Video slowdowns are related to missing hardware accelerated decoding (nvdec), it's not a libretro/PPSSPP Issue.
FMV cut-scenes will be fine.
Libretro Docs (important informations for this core): https://docs.libretro.com/library/ppsspp/
Official Game Compatibility Tracker (your mileage might vary): https://report.ppsspp.org/games
GitHub (WIP Switch):https://github.com/m4xw/ppsspp/