I have been working on PlayStation 1 homebrew SDKs [1] and tools over the last year. Unlike other retro consoles - especially Nintendo consoles - the PS1 gets almost no attention at all; "PS1-style" games made using Unity or Unreal Engine seem to be decently popular, but nobody wants to bother with the real hardware anymore. Which is a shame, as the PS1 is a relatively simple platform which can be found for relatively cheap and offers a bare metal development experience reminiscent of modern 32-bit microcontrollers, with some interesting graphics and audio hardware thrown in. It is a platform unencumbered by the tile/sprite and storage limitations of the 8- and 16-bit eras, yet still limited enough to be a breeding ground for creativity and at the same time easily expandable with custom hardware through its integrated serial port and ISA-like parallel bus.
[1] https://github.com/Lameguy64/PSn00bSDK