I've used Meshtastic as small (5000-ish person) festivals, and even with higher bandwidth settings and stock rubber ducky antennas, ground to ground ranges through trees and people of around 1km worked just fine (with the expected shadows behind hills). This was only a small number of devices, I have no idea how badly performance would drop off if 10% or 50% of the attendees were trying to tx/rx Meshtastic or LoRaWAN signals.