Not necessarily; the same remoteness that made cell signal sparse likely makes ADS-B ground stations unlikely. There has to be one in range for it to show up places like FlightAware. Plenty of dead spots; you can help expand the network! https://www.flightaware.com/adsb/piaware/build/
I have an ADS-B receiver on a computer here, and am overhead a number of flight paths for JBLM.
The above comment is accurate, plenty of local training helicopter flights will be fully or partly dark (lights and/or transponders off), looking at my receiver's raw output stream.
