This all works great with no local SIM cards or other subscriptions or infrastructure needed.
We plan to run experiments with Reticulum when we stop for the cyclone season. Reticulum would open a lot more possibilities with both LoRa and internet-based comms. The Columba app seems to do a lot to bridge the usability gap, but work will need to be done to integrate Reticulum with our boat systems the way we have with Meshtastic (alerting, telemetry, digital switching control).