An issue was created on GitHub regarding dgVoodoo2 support in Proton in general, but it was closed, because it was considered "out of scope": https://github.com/ValveSoftware/Proton/issues/3516

Although I understand the focus on Direct3D games, particularly more contemporary ones, it's still a shame.

But as others in that GitHub thread mentioned, this effort might be worthy of a dedicated separate open source project. Namely an open source Glide wrapper that could also be combined with Proton.

I do not know if Linux or Proton is on the author's radar or not

No, it's not. Btw, if the same works on Windows then it's not a dgVoodoo bug anyway.

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I'll take the bait.
This isn't slashdot, please leave the hyperbole off these forums. Thanks

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What I forgot about: if, for any potential reason, you run dgv Glide through DX11 at feature level 10.0 then mipmapping is indeed disabled "by design" because of certain limitations.