Anarcute (390720) doesn't recognize gamepad

Compatibility Report

• Name of the game with compatibility issues: Anarcute
• Steam AppID of the game: 390720

System Information

• GPU: nVidia GeForce GTX 1050
• Driver/LLVM version: nvidia 410.73
• Kernel version: Tested on 4.15.0-39 (Ubuntu's official repos) and 4.19.x (Ubuntu's Mainline PPA)
• Link to full system information report as Gist: https://gist.github.com/Yowlen/1d5ad971119b6363c6c8cfa6444a5783
• Proton version: 3.16-4 Beta

I confirm:

• that I haven't found an existing compatibility report for this game.
• that I have checked whether there are updates for my system available.

steam-390720.log

Symptoms

I have an XBox 360 gamepad plugged in and set up for use in Steam, but it's not recognized in Anarcute. From what I can find on ProtonDB, it seems to happen with all controllers, but I can only test and verify with an XBox 360 one.

Beyond this issue, this game works perfectly and barring some driver/Wine regression, should be able to be whitelisted afterwards.

Reproduction

Plug in a controller.
Configure Steam to use it.
Start Anarcute.
Try to use it in the game.

Start with the attached steam-390720.log and the listed reproduction steps, using the reported Xbox 360 controller setup and Proton version as context. Investigate why Anarcute does not recognize the controller; the issue is done when the game accepts controller input under the reported setup.