Hey @rnnr, thanks for letting me know. To be transparent, it's not likely that I'll fix it any time soon. What kind of gamepad are you using?
It's a shame, because your game looks nice :) and it already seems to work in menus, but I'm fine with that, I like to try games, but have also other things to do :).
I have Logitech F310, actually two of them, which works quite well on Linux via xpad kernel module. If you ever decide to try to fix it, I'm willing to help by collecting more info. Not sure what, though.
Thing is I couldn't reproduce the issue in build, and by the sound of it it's not a controller support problem (since it works in the menu)
Any chance you might have tried to play the game in BOT PARTY mode only? (Which is basically event demo mode with CPU players only)
Did you encounter the screen where you can select characters? (that's when you controllers are supposed to be joined as players if the game detects any input from them)