The main question is you want your friends to communicate each other inside or with you and others outside Russia? For outside there's no better alternative than cleverly configured VPN (+Tor). I really don't think Nostr based thing can do much here. Maybe if we had enthusiasts who creates relays on critical infrastructure from "white lists"... and it still easy to block. At the moment I'm testing Delta chat - there's a chance emails won't die when other communication channels will be turned off. But centralized services (Yandex mail, Mail. Ru etc.) can easily ban accounts that transmit encrypted messages using Delta Chat, citing suspicion of spamming, so again, relays within the country are needed.