You mean games that arent available in steam at all, vor those which you haven’t bought there? I found the easiest workaround for me was to simply add the games to my steam library and to launch it from there. Then I don’t have to worry about what proton version I should use or whatnot.
We had a TV report about a photographer who actually transfered big files with via horse because the transfer over the internet was slower than a calm ride. (Germany - 2021) link for Germans