The LoRa enthusiasts in my area seem to all have moved to Meshcore, largely because of a quirk in Meshtastic's routing algorithm that doesn't handle nodes with widely varying visibility/power/noisefloor well. They report regularly getting traffic hundreds of miles. There might be a couple mountaintop repeaters in the mesh though.

For OP's situation I think runners and a store and forward system like Scuttlebutt/Briar/etc might work better. But I'd love to see a couple of thorough case studies on that kind of system, they've been around for many years targeting related scenarios.