https://bugs.winehq.org/show_bug.cgi?id=40907
--- Comment #4 from Sten_Gun robenfi@gmail.com --- (In reply to David K. from comment #3)
Still does not work with 1.9.22-staging. Having vcrun2013 installed seems to make no difference. Keep in mind this is about the new client that is currently under development - the old one works fine.
I know is the alpha client, but I use it and I start it with success under wine.
This new client is based on Chromium (CEF), which is known to make problems with Steam due to its sandboxing. So it seems quite possible that this is the problem here.
However, since the new client will soon be the only way to play the game, it might be good to find a fix or at least a workaround.
I forgot to mention that you have to disable cef sandbox, otherwise the client will not start. This is how I start the alpha client
WINEPREFIX=~/.wineLOL wine LeagueClient.exe --no-sandbox
vcrun2013, dotnet2 and dotnet4 installed on this prefix, plus the required stuff to run the main game.