HP Reverb G2: Trigger doesn't work

[septagram]

Having trouble getting the game working on my HP Reverb G2, in particular, I can't shoot with the trigger

• Trigger works fine in menu
• In "Customize controls" I can't set it for the fire action
• ...even if I tell the game to disable controller input in menu
• And there's no trigger axis in the joysticks menu too

I can assign buttons on my controller to shooting, but that's quite awkward and doesn't feel the same, so I'd really prefer to shoot with an actual trigger.