This is a pretty minor thing, but with the open sourcing of WinUI, I wonder if there's enough open-sourced that people could try and figure out how to support Dark Mode themes in non-UWP applications?
As of automatic detection check my question on SO: https://stackoverflow.com/questions/51334674/how-to-detect-w...
I myself implemented the modern black menu style for a tray icon, so that the menu looks like the native tray icons. It's "just" a matter of owner drawing everything. Unfortunately, there is no secret "make my app dark" api in WinForms / WPF.