I think the main competitor to the Pico is the various ESP32 series boards that are out there. From earlier generations there are still variants of the Blue Pi

I think the main competitor to the Pico is the various ESP32 series boards that are out there. From earlier generations there are still variants of the Blue Pill at maybe $2 per board. I could imagine using a Teensy for something more serious where the cost was justified. But, I think we need a successor to the Pocket Beagle, or maybe a cross between the Pi Zero and the Pico.