Very nice - and so clean!!! - build, it's impressive!
Could you tell us what you used as push-buttons behind the L&R keys? I'm building up my cart on AliE. and I would be interested (for now I chose
these because I wasn't sure what to use under the L&R buttons of my cheap-fake-SNES controllers).
Also, I was told somewhere that only the Raspberry* would work with Retropie/Recalbox. Do you mean that we could use NanoPi Neo Plus2 SBCs as well??

It would be soooo great, because it is so much more powerful than the RPi Zero...!