Hi! I have been looking around without finding any solution regarding GameCube.
According to the Board Compatibility GameCube should be able to run on PCx64. I have put the roms in the recalbox\roms\gamecube folder with ISO files as the readme says.
There is no info in the bios readme what bios MD5 that should be used but when looking around the internet FAE2B558FFC344467170520D62177E5C is the MD5 for the US IPL.bin file that should be used but since there is no info on the recalbox documentation I do not know if this is correct.
I can see all the roms on the PC with recalbox-x64 6.0 installed but when I try to boot a game it just becomes black for a short time and then sends me back to the gamelist.