It is fundamentally not possible to have strong privacy or censorship resistance on proprietary operating systems like iOS and Android if a state is targeting y

It is fundamentally not possible to have strong privacy or censorship resistance on proprietary operating systems like iOS and Android if a state is targeting you. Even the so-called open source Android ROMs have no choice but to include hundreds of privileged binary blobs to make the proprietary hardware work. All a state actor need do is leverage their no doubt existing backdoors into said binaries and all plaintext is revealed on those devices. They could also issue a secret order to mobile app stores to issue slightly tweaked Signal binaries. In either case Signal would never know that users are compromised. For my own company which does security research, privacy is critical. We bring in only people who have been trained to only access the channel from dedicated QubesOS VMs, with no mobile access permitted. This is not perfect but it is as reasonable best effort until we can run Matrix home servers in a TEE (working on foundations for this atm). Signal by contrast demands a phone number and assumes mobile handsets can be fully trusted so it already has ruled itself out for high risk use cases. Matrix on the other hand I can run a private server of, and enforce whatever rules are appropriate for my threat model.