Played for a few hours and it works flawlessly.
Ubuntu 18.04.1 Proton 3.7 Kernel 4.15.0-32-generic Radeon R9 380
System information: https://gist.github.com/GitoMat/16d14cbe2db371fb245b750d442aea94
Found in the 2018-12-11 white list update.
proton 3.7
Played for a few hours and it works flawlessly.
Ubuntu 18.04.1
Proton 3.7
Kernel 4.15.0-32-generic
Radeon R9 380
System information: https://gist.github.com/GitoMat/16d14cbe2db371fb245b750d442aea94