https://bugs.winehq.org/show_bug.cgi?id=21232
--- Comment #51 from William Feely BFeely@aol.com --- (In reply to Aaron Franke from comment #50)
https://www.youtube.com/watch?v=F4Zoiyfk9v4
An update to the Steam client, which will likely be coming soon, will use the Chromium engine for the library. This means that every single function of Steam will use web UIs and Steam will become useless in Wine. When this happens, every single Steam game will become unlaunchable in Wine via normal means.
Because of this, I think this needs to be elevated to Wine's #1 priority issue.
Considering that the alpha can be enabled by downloading a file from the Steam CDN and using a special command line, I suspect Steam may still have for at least a while a fallback mode.