https://bugs.winehq.org/show_bug.cgi?id=47198
--- Comment #106 from Manuel mail+wine@m-reimer.de --- With the last update of the LoL client the Wine version, used so far, no longer is able to run the client. Most probably because they updated to CEF-91.
A up to date wine-staging can start the client but then will not allow to actually play the game. So this issue seems to have been fixed with later wine-staging versions.
I also tried with regular Wine (GIT-version from today) and this also fails to start the client. So whatever fixes this has to be a staging patch.
So maybe that's a good point where someone with the required knowledge could try to port the patches to a more modern Wine version?
The only alternative, I can think of, would be backporting whatever wine-staging patch is needed. But, so far, I haven't found the correct one and I'm not sure if backporting will be possible at all.