Layer your backups and you'll rarely be truly cut off. First layer: offline preparation. Download offline maps for your whole region and an offline translation pack before you need them; both work with zero connectivity and cover most everyday emergencies. Keep key documents, bookings, and emergency contacts saved locally on your phone, not just in the cloud.
Second layer: network redundancy. A SIM from a second carrier, or a spare travel eSIM, means one network's outage doesn't strand you, since it's rare for all carriers in an area to fail simultaneously.
Third layer, for genuinely remote travel: newer phones increasingly include satellite SOS or satellite messaging features, and dedicated satellite messengers are the standard for trekking far from coverage.
Finally, register your trip with your embassy's traveler program if your country offers one; during disasters, embassies use those lists to account for citizens and can assist with emergency communication to family.