Has anyone had any luck replicating their Proton setup outside of Steam? Or simply just running a Proton game outside of Steam after getting it set up using Steam?
I have run many Windows games outside of Steam.
I prefer to set up each one manually: Create a Wine prefix, install the game (or copy it from an existing installation), install a few key libraries like DXVK and a Visual C++ runtime, make a launch script with game-specific environment settings or launch options. Tools like Lutris and Bottles can automate much of this, in case you need a little help or just find a GUI more convenient.
This is my usual approach to non-Steam games (especially GOG), but even Steam games can be convinced to work offline with the help of a Steam emulator. It wouldn't work with a game encumbered by DRM (e.g. Denuvo) unless a cracked version could be located, but in my experience, that's a minority of Steam games that I categorically avoid in the first place.
So, I'm not worried about my game library vanishing if I ever lose access to Steam for whatever reason. Most (if not all) of it could be recovered with a bit of effort.
I would be interested in a project like this if it were a distributed network.
It's important to ensure that accumulated community knowledge will survive, and conversations can continue, when an instance dies or becomes intolerable. (Reddit and Stack Exchange have recently brought this into sharp focus.) It's so important that I no longer contribute to sites like this unless they provide those assurances.
So I hope this one develops into something that meets that need.