In Russia, we use Telegram for communications. More rarely Vk[dot]com.

However, I have Instagram, Facebook, discord (although it is blocked, but I usually manage to unblock it quickly). If you want anonymity, you can create a mail in the Tor network. However, for now we (in Russia) do not need to hide much. Someday we will find people who are deeply knowledgeable about information security and will investigate the issue of anonymity on the Internet, but for now we are operating legally.

I wrote you a letter. “Hello to you, unknown comrades.” If you didn't get it, write to me here.