@gwennelsonuk well there is PsNee, which is an opensource modchip firmware that runs on arduino.
i suppose you could theoretically reduce a lot of that complexity by rewriting it for rp2040 or something.
there's picostation, which is opensource firmware running on an rp2040. does optical disc emulation on the real console, letting you boot from sd card.
finally, there is https://github.com/Lameguy64/PSn00bSDK open source devkit
modchip still ideal to defeat the mechanon wobble check; can disable from bios