This is actually a really good development. So far I have found that the best way to run non-Steam games is to add them to Steam because using Proton outside of Steam is not recommended.
So if Steam ever becomes worse for whatever reason, it is good to know there will be alternatives.
Not sure if they used it for other languages but this was the cover for the Dutch translation of The Lord of the Rings I had as a kid.
https://media.s-bol.com/3o5KqAGL64r/534x840.jpg