Microsoft rust is not that much worse than c++.

That said, it seems some people get nice results at porting from c++ to C using "AI" (LLM?).

If fltk had C bindings it would have been a thing long ago, because usually C programs will run faster than their C++ counterparts. DIllo's requeriments would be far smaller (and Dillo runs on potatos, I won't be surprised if it still runs on i486 machines)