All I did today was label the file btcg_win.exe as a Windows executable in the itch.io back-end. I didn't make any changes to the files themselves, so I don't know why this would break something for you.
Do you want to try downloading the game from the website without using the itch app and see if that works?
I tried that, and ran into the same problem where it crashes when it tries to install Microsoft .NET. However, I think that this might be because I had a much older version of Wine installed on Linux than I had realized; when I upgraded to to version 10 (from version 6) everything ran much more smoothly. It's weird that it had been working fine until today, though...
(Just to be clear, I do not expect you to spend a lot of time supporting Linux users! Also, I just bought the game so I could throw a few bucks your way and get a Steam key at the same time, and the experience on Steam on Linux has so far smooth as well.)
