> Can I transfer my Overwatch battlenet account to steam? I really want to jump ship too.

Seems like you can just keep using the Battle.net account on GNU/Linux. You just add the Battle.net installer as a "non-steam game" (bottom left of the games list). Then, you start it, add your account, install the game and it "just works". I used it on the steam deck to play D4 beta and D2R on my CachyOS desktop.

> How is Proton with nVidia drivers? I have a 3080.

My battle-hardened 1060GTX served me for years. I recently upgraded my whole rig from Debian + Intel + Nvidia to full AMD and the RX9070XT works very well, with the caveat that I had to switch to a newer kernel on CachyOS to support it. That was 4 months ago and the situation now should be resolved, so you can prob use any old normie distro.

Thanks for the tips! I will try when I have some time.

Any chance of triggering anticheat on battlenet if I do this? Like does Blizzard has an official stance on it?

You can also add external games to launch via steam too, so you might be able to do it without transferring.