Yeah, for example embassy-rs is an RTOS that uses rust async on tiny microcontrollers. You can hook task execution up to a main loop and interrupts pretty easily. (And RTIC is another, more radically simple version which also uses async but just runs everything in interrupt handlers and uses the interrupt priority and nesting capability of most micros to do the scheduling)

Sorry for nit but embassy is not a RTOS (or any OS), its a framework

Interesting references, thanks. Moss seems to be doing the same thing as Embassy.