Electronjs does the 3 Desktops (linux,windows,macos).
Tuari is new, serves the same user base, smaller, but you need learn Rust.
Flutter does 3 Desktops and 2 Mobile platforms(android,ios), but you need learn Dart.
While doing my own research, I eventually chose Flutter, reasons are:
* it does 5 platforms fairly well
* its user base keeps rising rapidly over recent years
* dart is very much java|c++|javascript syntax alike, just simpler, picking up dart at least is much easier for me comparing to Rust.