The RP2040's PIO is awesome. Here are two retro-related projects I did in the last ~year.

You can capture video in a weird format with PIO on one core, and output it with PIO (in a standard format like VGA, or even DVI) on the other core, like here: https://blog.qiqitori.com/2022/09/raspberry-pi-pico-15-6-khz...

Or you can implement old DACs that expect a weird input data format, to a certain extent, like here: https://blog.qiqitori.com/2023/03/raspberry-pi-pico-implemen...

(Now I'm almost at the end of my sabbatical but think these projects (and others) were totally worth doing even if it meant living off savings, heh.)