Define "serious"? Every so often I have a need for a small cheap device interoperating with a larger system that I'm developing. Like something that sits on MO

Define "serious"? Every so often I have a need for a small cheap device interoperating with a larger system that I'm developing. Like something that sits on MODBUS and does a simple task when signalled. I've taken the RP2040 and Pico board and spun it into a gizmo that can do whatever I want with Micropython, and it's an order of magnitude cheaper and faster than trying to spin it up in STMCube.