Something similar happened to me with Doom 64 and it stayed like that for a while, until Proton 9 was released. There was also a temporary solution but I don't remember what was it. Though you probably can find it on Doom 64's ProtonDB page.
You can try GE-Proton from version 9 I guess, unless you haven't already tried that.
At least nowadays it's so much easier to find FreeDOS laptops. I remember that it was not a thing here 20 years ago, and Windows was included in the warranty so you couldn't remove it for at least 2 years (if you care about warranty).
I feel like some people would still use them with their noses out so I'm not sure it will be really different. :)