Anything to make gaming easier, especially non-Steam. I'll list what I know of so far:

Bottles.

Faugus Launcher. UMU-Launcher GUI, which is kinda like Bottles but for proton specifically instead of WINE. It's early dev and lacks functional GameScope for now, but Bottles I noticed really doesn't like me using proton so this was an alternative I found.

This is a unified launcher for Windows games on Linux. It is essentially a copy of the Steam Runtime Tools and Steam Linux Runtime that Valve uses for Proton, with some modifications made so that it can be used outside of Steam.

MangoHUD of course.

Heroic Games Launcher.

Lutris.

I have Itch.io's launcher too.

ProtonUp Qt - grab various versions of WINE or proton for all these applications.

Winboat - Trying some experimental fuckery to use Vortex but I've not got that far yet, just got Winboat itself set up so far. edit: It worked surprisingly, modded Skyrim Special Edition, see my other comments here.