What's funny is that supporting high DPI on a winforms app isn't even hard. Even if you size all your widgets in pixels, if you just do a little playing with the scaling options and just try out the ui on high DPI, it seems to work pretty well except for the old icons. I forgot what the setting is called, but theres a (non-defaukt) scaling option or two that seemed to "just work" as it were.

The harder part is to consistently fix everything that uses the old win2000 8pt default font instead of a modern one.