@papadeltasierra BTW the ESP32c3's USB mode is disabled; unless you enable it, it should run as a standard serial port (which is what I am now seeing).
@papadeltasierra Aha, there is indeed 4 MB of flash! You need to use idf.py menuconfig and then set the Serial flasher config to 1Flash size 4 MB and then use Partition table to select a 4 MB usable partition table.
OK, can now confirm that an ESP32-C3 project built using the Espressif esp-idf framework can be uploaded to the T-ZigBee board. You will need to use the latest esptool (now a PyPi package) to ensure that the chip can be set to esp32c3.