Same issue here. Oddly enough, moving the mouse slowly makes the pointer move in a somewhat continuous manner.
I have this problem too! If I move the mouse very slowly it works correctly, but if I move it a bit faster (maybe a bug with mouse acceleration? although I have my acceleration profile set to flat) the FPS go to practically 0 until I stop moving the mouse.
It's not a problem with Doom 2016 though, it's global for Proton, at least for me.
Fedora 31 KDE with Nvidia GTX 770 driver 440.59. I have a Logitech G502.
This issue is fixed for me in Proton 5.0-3.
Fix high polling rate mouse regression.
That did the trick, it seems.
proton 5.0-3x1 2020-02proton 4.11-12x1 2020-02
Compatibility Report
System Information
I confirm:
NOTE The following .zip file is not a ZIP file, it's a
.tar.xzfile. Github did not let me upload a .tar.xz file, and it compressed to 2mb compared to 6.5 for ZIP. I had 169mb of logs for Doom, including for custom Proton versions like https://github.com/GloriousEggroll/proton-ge-custom version 5.1 and such. The problem exists there as well.steam-379720.zip
Symptoms
The mouse in game, both in the menues and during play, both using OpenGL and Vulkan, lags considerably. It takes me a good minute to move the mouse from one end of the screen to the other.
Mouse movement is not uniform either.
This problem does not exist using Proton 4.11-12.