I dabbled (briefly) in it, got flutter app running on windows + linux, though certain integration factors (smooth window resizing, stability, mouse wheel support, etc.) were not there yet.
For some of them (mouse wheel, keyboard, tabbing) there might be more work needed (and maybe not seen as important), but it could bring a real "electron" killer, where my slack, teams or whatever else "electron" app does not spawn 5 processes, and take GB of memory (granted, flutter still takes a lot, compared to leaner Qt, and much much leaner write directly using Win32), but then there are some sensible limits, and going below these (for the sake of perfection) doesn't buy you much nowadays (I no longer have to run QuarterDeck QEMM to shuffle my 640kb DOS+EMS memory efficiently around :))