Talking about RP2040 powered controller firmware. GP2040 is an amazing project, which is used a lot in the Fighting Game Community where custom controllers are common. https://github.com/OpenStickCommunity/GP2040-CE
(I'm lead software dev on it)
I’m kinda burned out from always having to replace and hunt for parts for my gc controller because of my almost 22years addiction for SSBM.
Considering getting a phob soon :)
I once tried putting an Arduino in an arcade stick, for reading controller inputs and sending keyboard presses via USB, but the lag was horrible. It's been on my to-do list to eventually dive enough into AVR-C to try to improve on it.
There is/was a premade board for this (don't remember what it was called), but it was quite expensive, and I didn't want to keep moving it between controllers.