Yes! If you leave the default channel enabled it will join the public meshtastic network. But you can run eight channels at once, and the others can have different encryption keys.
The default setting is also to forward any received packets to the mesh, even ones it can’t decrypt.
For a good compromise, use Meshtastic. Long-range radio mesh network for texting that phones can use instead of cell networks.
Can one make a general relay meshtastic node, or are they all private relays?
Yes! If you leave the default channel enabled it will join the public meshtastic network. But you can run eight channels at once, and the others can have different encryption keys.
The default setting is also to forward any received packets to the mesh, even ones it can’t decrypt.