I’ve been using retroarch with the Genesis Plus GX core, and that seems to work well and is open source. Not everyone loves retroarch, but I’ve moved to it so I can use some of the more interesting HDR 4k CRT shaders

One warning, if you use a display over HDMI, then you might have a bad time with Radeon on Linux. I use an LG C2 TV as my monitor, and there is a bug in the driver that forces it to a crappy ycbcr mode that ruins text clarity. I did try all manner of workarounds like hacking up the EDID profile, but I gave up and went back to Windows for now.

It’s a very specific issue, but a showstopper if it affects you

Nope, it’s not. It’s in the terms of service. If you don’t like that, don’t sign the contract with them. Steal it if you want to. I’m cool with piracy, just not with the poor attempts at justification.

This is why I only carjack rental cars, it’s totally not stealing!