Last year I decided to finally break out of the browser and get into actual PS1 homebrew. Unfortunately the state of the scene wasn't, and to some extent still isn't, that great: most homebrew games are still made using what's basically a modded version of the original Psy-Q SDK, which is rather limited in many ways. I started contributing to an open-source PS1 SDK instead [1] by first adding a dynamic linker, then revamping the build system entirely and now building a custom high efficiency FMV playback library (totally not inspired by pl_mpeg of course) that combines the hardware accelerated MJPEG-like decoder with the GPU's alpha blending capabilities. I'm also working with a few other people on reverse engineering one of the most famous PS1-based arcade systems, the Konami System 573.
It's a shame the PS1 isn't receiving the attention other consoles are getting in the homebrew scene. The hardware is architecturally simple yet powerful [2], but I guess nobody wants to fiddle with 120mm polycarbonate circles anymore.
[1] https://github.com/Lameguy64/PSn00bSDK [2] https://www.copetti.org/writings/consoles/playstation