I don't know of a competition, but there is an 8-bit retro discord server: https://disboard.org/server/643973143358341151 https://disboard.org/server/6439731433

I don't know of a competition, but there is an 8-bit retro discord server: https://disboard.org/server/643973143358341151 https://disboard.org/server/643973143358341151 Various projects get shown off, plenty of boards built around retro (and quasi-retro) CPUs, some more audacious stuff like rebuilding the Apollo Guidance Computer. The ultimate homebrew derby is those brave enough to make their designs available for sale, I suppose.