Microsoft announced .Net Core 3 comes with WPF and Windows Forms. So can I create a Desktop application for Linux or Mac using .Net Core 3?
Although it is not native dotnet core on linux, but it may be helpful - using wine.
I find a very useful comment in the discussion here, more details here
In other words, it is possible to use windows version of dotnet core under wine.
I didn't try it yet, but from the article I mentioned I can say it looks nice and might be an option.