Whilst Briar is an excellent P2P messaging client (requiring no Internet) it still does not yet run on iOS. So to be able to connect to everyone, you want to consider clients which do connect as widely as possible. As with all P2P clients, your friends all need to also have the same app installed. Usually these clients require zero personal information (not even a phone number) to be used.
Bridgefy is designed to work on local Bluetooth (max about 100m) during natural disasters, a protest, at large events, at schools, etc. It will create a mesh network, so one or more other peers can help transmit messages further. See https://bridgefy.me/.
Jami also is a P2P client, but it uses encrypted TCP to communicate. It can be installed on Android, iOS, Windows, Linux, macOS, and Android TV. It will connect over the Internet to any friend, with no servers required (there is no website that can be blocked or intercept messages). It does not work across Bluetooth, but it can work on a local area network (without Internet) if everyone is on the same network, e.g. a Wi-Fi network. So yes, typically something like Jami will work perfectly in Russia or Ukraine across an Internet where servers are being censored or blocked. See https://jami.net/.
These are pure messaging apps though, so if you want P2P blogging you'd want to consider RetroShare, Secure Scuttlebutt, Aether or other similar service that works without any websites or servers at all.
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