Note: The game does not work on MX Linux 17 Horizon, but I know that is not a distro officially supported by Steam like SteamOS or Ubuntu.
With the new beta Steam client update (v1535402532) gamepad works again ingame on SteamOS BPM :)
Nothing extracted yet.
Without counting the new issues with the generic USB controllers of the last Beta Steam Client updates, I've tried this game and after that played like an hour flawless (in Steam Client version 1534892652) like you can see in the video linked here
OS: SteamOS 2.0 update 1:2.154
CPU: AMD A10-7870K @ 3.9GHz
RAM: 8GB (6.7GB usable)
Steam Client Compilation: Aug 21 2018, 22:37:21
Steam Version: 1534892652
Video: AMD Kaveri 1GB
Driver: 3.0 Mesa 17.2.4
Gamepad: SEISA SJ-702 USB (Play Station 2 like)
The game still works just fine (tried a little more a while ago with a keyboard)