These are charts for LTE coverage. You might be more interested in a 3G chart, which is sufficient for safety in wilderness and will have more coverage.
Which sucks because I can get a 3G module for my iot projects for 5$ and I think 4G modules start at 50$?
Are we just at the mercy of 4G now for services that need large coverage but low throughput? I know 5G technically has a spec for IOT type stuff but I haven't seen anything about it, and I haven't seen modules for it.