Can you link to one that has individual virtual memory processes where the memory isn't freed? It sounds like what you're talking about is just leaking memory and processes have nothing to do with it.

Tbh on such a bare bones system I would use my own trivial arena bump allocator and only do a single malloc at startup and a single free before shutdown (if at all, because why even use the C stdlib on embedded systems instead of talking directly to the OS or hardware)

RTOSes I'm aware of call them tasks rather than processes, specifically because they don't provide the sort of isolation that a "proper" OS does.

Why is something running on an rtos even able to leak memory? If your design is going to be dirty, you've got to account for that. In 30 years, I've never seen a memory leak in the wild. Set up a memory pool, memory limits, garbage collectors or just switch to an OS/language that will better handle that for you. Rust is favored among C++ users, but even Python could be a better fit for your use case.