This project’s last update was 2017, but it seems to have got a good distance before going quiet. For CPC, MSX, PCW Joyce and Enterprise machines:
SYmbiosis Multitasking Based Operating System
Preemptive multitasking - 1024 Kb dynamic memory - 2 terabyte filesystem - 100% flexible windows GUI - network capable
available for your Amstrad CPC, MSX, Amstrad PCW and Enterprise 64/128
According to these facts, it’s a microkernel design.