Beyond Divinity fails to launch without PROTON_USE_WINED3D

Issue transferred from https://github.com/ValveSoftware/Proton/issues/4466.
@realnc posted on 2020-12-13T06:00:23:

Compatibility Report

• Name of the game with compatibility issues: Beyond Divinity
• Steam AppID of the game:219760

System Information

• GPU: GTX 980 Ti
• Driver/LLVM version: nvidia 455.45.01
• Kernel version: 5.4.83
• Link to full system information report as Gist: https://gist.github.com/realnc/b4167a5632217e08c099c3dff1fb4f3a
• Proton version: 5.13-4

I confirm:

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

I am unable to post the steam-appid.log because even when following these instructions:

Please add PROTON_LOG=1 %command% to the game's launch options and drag
and drop the generated $HOME/steam-$APPID.log into this issue report

there is no *.log file generated:

$ ls ~/*.log
ls: cannot access '/home/realnc/*.log': No such file or directory

Symptoms

Trying to launch the game results in an error dialog saying "Not enougth texture memory."

It is necessary to use PROTON_USE_WINED3D=1 %command% in launch options for the game to run.

Reproduction