WPF is really interesting. There are a few projects which are Windows only that have expressed an interest in doing a Linux release, but since WPF only supports Windows they haven't thought it worth the time to port it over to something like Avalonia. The Xenko game engine is one such project (although their build system would also need work).Announcing Open Source of WPF, Windows Forms, and WinUI at Microsoft Connect(); 2018
Looks like parts of .Net Framework are going open source. Could be a good thing for wine-mono.
I imagine some third party will be trying to get WPF working on Linux now, so maybe these projects could have a better chance of coming over too.