If you travel a lot in bad cell areas, a GPS-only unit with a built in map is very reliable (e.g. various Garmin products), and can be inexpensive as in sub $30 (tons of them on eBay).
I guess I have to revive my Tom-Tom GPS (v6). Rural area is slow to change, so map change is not as much a problem. I will have to test if the battery in eat can still hold up.
I thought Google Maps used live (i.e. mobile data or WiFi) map tiles? Or have they changed that now?
I too use OsmAnd, in fact often prefer it to Google unless I want to see Streetview or Sat view, but only for mapping, I've never tried it for navigation TBH.
For navigation I use Waze which caches map tiles when you plan a route but obviously you need a data connection before you start out (which probably fits most usage cases) after which it's happy working offline.
re: "I thought Google Maps used live (i.e. mobile data or WiFi) map tiles? Or have they changed that now? ... ..."
I think the change may be the other way around. Downloaded map worked for me for a few years. Once the destination location is set, navigation without data connection was no problem at all. I have my region's map downloaded. I did my destination selection on the downloaded map by touching the spot or search with WiFi (stopping at a coffee shop w/ WiFi or using my mobile hot-spot) then turn off WiFi for the rest of the trip. The rest of the navigation is the same as with WiFi.
During the lock down, I stop traveling outside my immediate area. Last weekend was the first time since the virus thing started (about March 2020) that I ventured beyond 30 miles from my house. It was also the first time I saw "Data Connection Lost" warning with Google Map. So I believe some time during the lock down, updates to the Andriod or to Google Map make constant WiFi connection a necessary thing.
Waze's caching probably wont work for me. For my immediate travel, I may not have a well defined destination but instead just a general area (helping someone with apartment shopping and looking around a target area).
I'm going to reset my device, restore to an earlier version of Google Map, see what I get.
Hey, guys, thanks for the suggestions. I appreciate it.