If anybody out there is dismayed by the rise of Electron for UI, crap like this is why that came about.
The "rise" of Electron has occured primarily because it allows people to do desktop development using whatever it that they learned in the context of web-centric development. For some people, that's an excellent turn of events, for others, it is a horror show.
Even if I was willing to grant that GTK and Qt etc. are "crap" (which I'm not, but ...), it's notable that there are essentially zero cross-platform alternatives that could be judged any less "crappy". Either you think that nobody smart enough has tried, or this is a much harder problem to solve to your liking than it first appears.
Native, cross platform, tiny binaries, JS transpiler in the works, Android and iOS support in the works. Destroys this...mess.
See MSEIde, which is directly X11: https://github.com/mse-org/mseide-msegui
"MSEgui is a complete independent Free Pascal widgetset. It does not use any other widgetsets like GTK2/GTK3/Qt4/Qt5. MSEgui interacts on Unix directly with X11 server (like other widgetsets do). On Windows, it deals with the low level Windows GDI interface."
Although a separate windowing set than Lazarus, both are enabled by the FreePascal compiler.
Lazarus does have a GTK backend as an option on Linux.
But I'm the author of a substantial cross-platform creative/media application, and not only do we not use any RAD tools, I don't think we could. So if you "destroy this mess", I'm not sure how we could do what we do. Very few "creative" applications use stock toolkits and RAD tools.
I don't use Qt, but QML and its associated tools look to me at least as good as Lazarus.
I am no GTK fanboy but if you actually look through the linked tutorial it's quite straightforward stuff and all you need to know is C. You can't get much simpler than some of the early examples except maybe in Tcl/Tk.
If you look through an Electron tutorial it assumes familiarity with a whole bunch of web technologies and it's not any simpler.
The reason Electron and the like are popular is because developers can take advantage of their pre-existing knowledge of these web technologies and have the option to reuse code between Electron and web projects.
My prediction is that we should be able to build prod-ready native desktop apps with it within a year or so
There are some "promising new up and comers", including libUI.
If you work in the audio software domain, JUCE is likely your go-to cross-platform toolkit.
I didn't have much luck with libui (crashes, missing features, etc), and various immediate mode alternatives just require too many dependencies and other work that made integration painful. Plus, Lua bindings for these were always stale. In fact, Lua binding quality is pretty poor all around, including GTK, Qt, WxWidgets, and FLTK.
Some other lightweight Electron-like alternatives also exist.