More generally, I’ve been wondering if something can be said about minimal requirements in terms of CPU/memory.
The most constraining fact is that SuperCollider is a multi-threaded program with built-in networking and therefore won’t run on a microcontroller without heavy modification.
As James has said, SuperCollider already works on Bela, which is the most barebones you can get at the moment.
(As a side note: Bela had to add their own audio driver backend. The way forward would to add a generic “plugin” driver, so that libscsynth be easily embedded into existing applications that manage their own audio I/O, just like with libpd.)
That being said, it certainly would be possible to create a stripped down version of scsynth that could run on microcontrollers, but I’m not sure if you would get much value out of it…