Oh no! Another launcher! Well, not quite. In fact, Unified Linux Wine Game Launcher (ULWGL) is actually meant to be used by existing game launchers like Heroic Games, Lutris and others on Linux desktop and Steam Deck.
So what does ULWGL actually do? This proof-of-concept idea was put up by Thomas "GloriousEggroll" Crider, who also maintains the popular GE-Proton compatibility layer. ULWGL is designed as a helper to properly run Proton outside of Steam, it's "essentially a copy of the Steam Linux Runtime/Steam Runtime Tools that Valve uses for proton, with some modifications made so that it can be used outside of Steam".
The idea is that other game launchers would use this so that all fixes and compatibility can be properly shared between them, thus making Windows gaming on Linux a whole lot easier with Wine/Proton. Protonfixes would be the same across launchers, anyone would be able to run games through Proton with no Steam required and basically it just unifies everything.
Sounds like a really great idea so all these launchers don't need to keep re-inventing a way to run games in Proton outside of Steam.