I have a visceral (possibly undeserved) hatred of C++, so WxWidgets and Qt are out; as it stands it looks like for what I need I'm stuck with Electron for my GUI stuff, since I don't want the JVM dependency.
While the stock look-and-feel is functional-but-bland on all platforms, modern Tk is completely customizable and can approximate native widgets: https://tkdocs.com/tutorial/windows.html#dialogs