Heroic is reasonably seamless - it integrates with GOG and your Steam library, and by extension Proton. Pretty popular among Steam Deck users.

https://heroicgameslauncher.com/

I use Lutris for that, a bit clunky (especially updating games) but it does work.

See the other two posts for recommendations, but be aware that neither of the options listed is at the level of experience Steam may have spoiled us with. My last try was 4 or 5 months ago and I ended up just going with a VM.

I have heard of alternative game launchers that will take care of launching Windows games (including GOG titles) under Linux.

But I usually just end up purchasing Linux games through GOG and Windows games through Steam.

Lutris the popular option. Heroic is another but is a chromium app fyi.