This page has a lot of cross-platform GUI toolkits, but it focuses on C++:
https://philippegroarke.com/posts/2018/c++_ui_solutions/
I've been drawn to wxWidgets (actual native controls on each platform) or JUCE (most of the cross-platform commercial Windows/Mac/Linux audio effects I've bought are made in JUCE). But I've not had a chance to give either a proper try.
Years ago I used to all my cross-platform work with Xojo, a kind of cross-platform Visual Basic. That actually worked well for me, but then you're writing code in the Xojo Basic language, and it had some odd file formats for projects (not just raw text source files like C++ / Go would give me). Once LLMs hit I felt I probably needed to move on from Xojo to something less proprietary: https://www.xojo.com/
You can build your core in Go or any other supported language, and write the UI in the Hypen DSL.
While desktop is still in the works and should be out in the next week or two, currently the alpha supports Native iOS, Android, Web and Web Canvas, and just like mobile, the Desktop will be _real_ native.
Otherwise I think its QT and GTK on C/C++ as the other option across the desktop operating systems, neither is native on anything but Linux but they also look OK but I think a lot of people would rather avoid C nowadays for application development.
https://webkit.org/blog/16547/better-typography-with-text-wr...
WinUI 3 is pretty decent. Have a look at first-party programs like PowerToys[1], or Windows Terminal[2].
Only partially true: macOS is supported, and one can fall back to the web. But you're right in that native Windows and Linux are still missing.
> Linux
Problem with Linux of course is that it's almost as fragmented as Windows, with Qt and GTK being the main toolkits, but a dozen more if you ask the wrong people :D I personally don't like GTK, to me it (well, mainly Gnome) looks and feels like trying to copy macOS without understanding what makes it great, but Qt is a toolkit I can get behind…