the non-bloat collective
Nitron
Nitron is a virtual machine and operating system aimed at running on higher end microcontrollers (such as the Raspberry Pi Pico, micro:bit, and ESP32). The OS doesn't run entirely in the VM, the goal is that the VM provides low level functions that don't take long to execute (so they don't get in the way of the VM's multitasking) and inside the VM there are drivers running that use these functions.
Source
Note: Nitron needs to be rewritten