WoW! Two questions answered in 2 weeks! Although the Hartley vs. Lunduke one wasn't serious.
Little confession, I wasn't using Linux when I asked the Warhammer question, but it was the only excuse I had to keep from switching. After listening to the podcast and watching some past streams you played with Raven, I blew out my Windows install and am now fully Windows free. (Don't ask about macOS).
I'm happy and sad to report that Warhammer plays fine using Steam Play, but there are no games listed in the multiplayer campaigns. I'm taking that as a sign that it will not work. I have not tried hosting a game yet, will get back to you when that happens.