Looks like you think only in windows and linux. Ok, but how much of your rust runs on freeRTOS or bare metal and on how many processor families? C? Runs on all of them. 6502? No Problem? 8051? Clearly! CRC16C? Yes. Eco32? yup. i386? Is developed to run C. Arm64, Arm? They too. They run Minix in their internal controlling hardware. Written in C...
Nextest works on a variety of platforms and architectures -- a lot more than x86_64 Windows and Linux. Porting to new platforms tends to be quite straightforward as long as someone's made Tokio work on that platform. (This is the power of abstraction! Turning MxN portability problems into M+N ones.)
C definitely has a place, but "Rust is not portable at all compared with C code" is simply not correct. A lot more Rust code works across Windows and Unix than C code does. Rust's portability story is different from C's, much better in many ways but worse in others. In practice I do think Rust ends up being more portable than C in most practical scenarios -- for example, look at how things like `eza` work on Windows, the number one developer platform worldwide.
Rust is not portable at all compared with C code.