Hello @namtsui, please add [`PROTON_LOG=1 %command%`](https://github.com/ValveSoftware/Proton#runtime-config-options) to the game's launch options, reproduce the regression, and attach the generated $HOME/steam-$APPID.log to this issue report as a file. (Proton logs compress well if needed.)
Thanks for the test @simifor. This got me prodding some more. I am on guixsd using nonguix to install steam. Running flatpak steam instead, I am able to connect like you experienced on proton 9. It seems like it could be...
@namtsui couldn't reproduce the issue on my computer, for me proton 9/exp/hotfix let me create a room without showing an error, though I didn't try actually connecting with anyone else  to the game's launch options, reproduce the regression, and attach the generated $HOME/steam-$APPID.lo...
There seems to be a network regression. I am unable to create a room. To reproduce, Network > Casual Match > Create Room prints "A network error has occurred." Here are my test results against various versions of proton....
So I have this weird issue with lines of dialogue where, when my character's name is mentioned in Libra of Soul mode (one of the story modes), the rest of the line of dialogue following is omitted with one odd exception....
Sysinfo: https://gist.github.com/NoXPhasma/d4aa3253640c214493066ef6f3d8b5bb I have to disable the Steam Overlay or the game will crash at the first screen. No matter which proton version I use. I can't provide a log file...