Reticulum works on microcontrollers. The rnode firmware that works on meshtastic boards https://markqvist.github.io/Reticulum/manual/hardware.html

RNode is a transceiver program installed on a LoRa board to allow Sideband, Meshtastic, etc. to connect to a Reticulum network over LoRa.

I think you’re looking for the C++ implementation of Reticulum made specifically for microcontrollers instead: https://github.com/attermann/microReticulum_Firmware https://github.com/attermann/microReticulum