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.

Judging by the direction things are heading, only approved services from so-called white lists will operate in the Cheburnet mode. These include the websites and applications of banks, taxi services, major delivery platforms, the national messenger Makh, websites and applications related to the government and authorities, state media, local video hosting service, streaming platforms and app stores, among others. They won't even need international DNS; there is a separate domain name system for the internal internet, from which addresses like YouTube, WhatsApp, and others have already been removed. It's unlikely that GitHub or GitLab will be included in the white lists. However, currently, the likelihood of a complete blockade and isolation from the external internet is rather low.