Technically not a distro, but give Bazzite a try. It’s probably the most hands-off gaming experience on Linux. Valve employees also make contributions to it.

IIUC, Q4OS only shares its source code on request. Furthermore, the Windows installer is a fork (or somewhat based on) WubiUEFI.

Q4OS still has a .exe installer though.

TIL. This is pretty cool. I wonder how much effort it would cost to make this a viable option for most of the popular distros.