A few other options to consider:
- Lightweight local web server + web page combo
- Native layer for each platform + shared business logic parts
- Some game dev engine could also work - Unity, Godot..
Which language and cross platform desktop GUI framework checks the boxes for being lightweight in terms of filesize and memory usage, has native controls, supports accessibility and uses retained mode rendering, and works the same ten years from now as the day it was installed?
If someone were to build an installable desktop app with buttons, checkboxes, inputs etc. (so not a video game) which language and GUI framework should they to use to please the memory and filesize conscious?