[southerntofu]

Tox is peer-to-peer chat, Dino uses the federated Jabber/XMPP protocol. So on Tox your identifier is your public key, while on jabber you get a user@server address (which is usually the same as your email if your provider supports both protocols). Nowadays people interested in P2P chat mostly use jami.net or briarproject.org, both really cool. Briar in particular uses both a gossip protocol for local conversations (like Secure ScuttleButt protocol) and Tor onion services for internet-wide communications.

Both XMPP and Matrix servers can also be run on your own device (p2p): in XMPP world it's more common for ZeroConf LAN chat (to chat with other peers/servers in the LAN, not internet servers), while Matrix project is spending some efforts on Pinecone based on libp2p/yggdrasil to punch through NAT and (if it succeeds) offer proper P2P internet-wide. They have different trade-offs: XMPP protocol is more lightweight but less consistent about eventual delivery of messages when some servers can be offline at any given moment (it was initially designed as a live message-passing protocol).