Though it is basically just a Linux system, nothing special about it aside from the instruction set. When i ported a DOS game i made some time ago to it[3] all i did was install Debian and Free Pascal on a MIPS QEMU system, make sure it compiles with SDL and package the binary in the package format its launcher uses (OPK, which IIRC is essentially a squashfs image).
[0] https://en.wikipedia.org/wiki/GCW_Zero
[1] https://en.wikipedia.org/wiki/Ingenic_Semiconductor
I'm sure there are a few asterisks to this, but the WRT54G (the iconic Linksys blue and black wifi router) has a MIPS 32-bit CPU that's ~4x as fast as the PSX and ~1/2x as fast as the PS2.
32MB of RAM that the PS2 had would be really tight for modern kernels.
https://openwrt.org/supported_devices/432_warning
But CPU-wise I don't foresee that ~300MHz MIPS would be any sort of major roadblock.
When WRT54G was available kernel was 2.2 or 2.4
I did have some fun with that kit, despite the typical monitor issues, even with a sanctioned distribution.