Here is a log of the game running without dgVoodoo, producing the black squares around gibs and particles.
These look like lines of interest from the log:
err:ddraw:d3d_texture2_Load Trying to load surfaces with different mip-map counts.
err:ddraw:d3d_texture2_Load Loading surface with different mipmap structure.
Possibly related: https://github.com/wine-staging/wine-staging/tree/master/patches/ddraw-IDirect3DTexture2_Load
I agree that dgVoodoo2 should be added to Proton, maybe on a special third-party folder to avoid mixing of closed and open-sourced components.
Nothing extracted yet.
Compatibility Report
System Information
Symptoms
Explosions and gibs have black squares around the sprites.
Reproduction
Generate explosions and gibs
The black squares are gone and are rendered correctly when using dgVoodoo2 (http://dege.freeweb.hu/dgVoodoo2/dgVoodoo2.html).