The only advice you can semi-safely give to dissidents that face state organized death squads is to hide and get new identities, and never ever reveal the old ones to anyone.
Signal will not make people immune to death squads, nor will any other technology. It was not that long time ago that members of Anonymous went after the cartel and we got pictures of people tortured and killed. It only take one trusted person who know a dissidents real identity or family or friends or community for things to get very ugly very fast.
If the PGP team promised security against state organized death squads then that's their fault. Pretending that technology will protect you against that kind of threat can be a very costly mistake.
