meshtastic
Almost 40km isn't too bad for a few mW at 868MHz and the stock heltek v3 antenna. With a larger antenna it does even better. What a surprise.
Here I'm using a pcb log periodic wedged in a sapling.
Turning on wifi disables bt. Worth knowing before you go out of range of the wifi n/w. Also worth knowing that you can connect with a cable and switch bt back on.