Whatever is causing the bug it's not your graphics card, I have the exact same bug with my Nvidia GTX 1650 & the latest drivers Linux Kernel 5.4 & Proton 5.0-10.
https://gist.github.com/lucifertdark/584c14275612e8e3c4a8070d428d8a02
I think DXVK missing support for the same kind of textures he mentioned in the quote. That said, I haven't tried wined3d yet.
Edit: Ok never mind, with PROTON_USE_WINED3D=1 the character turns black or the game crashes, if you start customisations.
Hello, Youropa dev here.
So from the log it looks like the driver converts some textures from ARGB to ABGR when creating/loading them. (D3DFMT_A8R8G8B8 becomes D3DFMT_A8B8G8R8 which the game does not currently support)
I'm not sure if there is anything the Proton team can do to fix this, but I am looking into fixing it.
Compatibility Report
System Information
I confirm:
steam-640120.log
youropa.log
Symptoms
Character customisation doesn't work. In the customisation menu you can't see the spray can or the customisation on the character.
Dev said to the same issue on windows "it looks like your graphics card isn't supporting all texture formats the game is using"