[kaspar030]

Also check out Ariel OS (https://ariel-os.org), which is built on top of Embassy.

[inferiorhuman]

Also Xous which is completely independent of Embassy but applicable if you're looking for preemptive multitasking:

https://www.youtube.com/watch?v=DaWkfSmIgRs

[IshKebab]

But requires an MMU.

[panick21_]

Well then: https://hubris.oxide.computer/