Essentially ULWGL will allow you to run your non-steam games using Proton, Proton-GE, or other Proton forks using the same pressure vessel containerization and runtime that Valve use to run games with Proton

This is the crucial piece of information. In less technical terms: Proton is designed to run in a very specific environment and it might be incompatible with your system. Steam runs Proton inside a bubble so that it interacts less with your system and so the incompatibilities don’t become a problem. ULWGL aims to create the same bubble so it’s the correct way to run proton.

From the naming it’s clear that GE wants this to be the new standard, but it’s not really a new standard. This is porting Steam’s launcher, which already exists, to non-Steam clients.

This is great. Proton is getting a lot of testing just based on Steam’s userbase and it is backed by Valve. We also have a lot of data on proton’s performance and potential game-specific fixes in the form of protondb. Making sure that non-Steam launchers can use all that work and information is crucial to guaranteeing the long-term health of linux gaming. Otherwise it is easy to imagine a future where proton is doing great but the other launchers are keep running into problems and are eventually abandoned.

One thing that I am curious is how this handles the AppId. If this AppId is used to figure out which game-specific fixes are needed, then it will have to be known. Do we have a tool/database that figures out the AppId from the game you are launching outside of Steam?

I don’t know of anything about nvidia being “way behind”, apart from wayland support. The only case I can think of the top of my head where the bad wayland support comes into play is if you have multiple monitors with different refresh rates. But maybe even that is not an issue anymore with new nvidia drivers. Maybe others can comment on it as I no longer have an nvidia card to check.

Use protondb to check whether your games play well on proton. It shows each commenter’s system specs as well, so you can see if a game has issues on nvidia specifically.

https://www.protondb.com

One warning: don’t try to install software, including the nvidia driver, as you would on windows. On linux, you don’t go and download it from nvidia’s website, you get it from your distro’s package repositories, and you let it get updated automatically via your system updates. Depending on the distro you install, it might be as easy as checking a tickbox to automatically install “Additional drivers” or “Proprietary drivers” during installation.

EDIT: I assumed “way behind” to mean that nvidia is behind amd on linux. If you meant how much linux gaming is behind in general, that’s another story. Linux does tend to lag behind in implementing newer features like newer DLSS versions. If you’re worried about this, then perhaps you will get more information if you post a question about what specifically you care about.