I've used RTIC in a few cases. In practice, it's a thin wrapper over interrupt handlers and locks on resources in them. These days, I prefer using macros to simplify the (natively onerous: many <> brackets with Mutex, RefCell etc.!) locking and initialization of global variables.

It also has software tasks, which is presumably the Embassy tie-in you mention.

So can Embassy -- look at InterruptExecutor.

>it can use your interrupt controller as a scheduler

Isnt' that how schedulers always work?