Proton 4.11-8 - RC Transmitters don't work inside games

Using Proton 4.11-8 I can't get my RC transmitters to work when connected to USB. They work in native games so I know it's not a driver / permissions issue. The game detects them but there's no input at all, or there is and it just spazzes out randomly. A DualShock 4 controller works perfectly fine as expected.
RC Transmitters I've tried:

• Jumper T16
• FrSky Taranis X-Lite
• A Betaflight Quadcopter acting as a controller

All of these are ARM STM32 devices acting as an HID device. I know DRL Simulator is using the Rewired Unity asset, however I'm unsure of Liftoff.

Games I've tested so far:

• Drone Racing League Simulator (had to run <Link removed by moderator> on prefix)
• Liftoff (native works fine, under Proton joystick does not)

I'm not sure if anyone here owns any of these joysticks, so if you need more debug info or anything let me know.

Reproduce the missing or erratic joystick input in Drone Racing League Simulator and Liftoff with the listed RC transmitters, comparing Proton with native execution. Start by reviewing the Proton joystick/input handling and the Rewired Unity asset context; done means the transmitters provide stable in-game input while the DualShock 4 continues to work.