A new article https://avtonom.org/blog/chem-ploh-telegram on why Telegram should be avoided by activists under authoritarian regimes and similar situations, as well as some mitigation measures for when it can't be avoided,
in Russian from Autonomous Action, an organization of anarchists and libertarian communists in Russia.
In particular if you know any dissidents, mobilization refuers, etc in Russia, please share this information with them.
Note that the link in the article to Partisan-Telegram Android is missing a colon so won't work clicking on.
It should have been:
https://github.com/wrwrabbit/Partisan-Telegram-Android