Check out 0xChat for secure group chats based on NOSTR: https://www.0xchat.com https://i.nostr.build/0HEZJMNVxeyHVmuT.png
"#SimpleX is the best for privacy, but I think it has occasional issues with groups. #0xchat runs on #nostr, but the privacy isn't that great yet. If you don't mind the lack of privacy, which #Telegram didn't have anyway, 0xchat is fine. Eventually, NIP-104 for EML will be finalized, and then 0xchat can implement it, and it'll be the obvious choice."