Magic Wormhole comes close. I don't think it 100% peer-to-peer since there's a coordination server, but that's not so different to most P2P programs on the internet, which need something like a STUN or ICE server (or port mapping) to get around NAT.

https://magic-wormhole.readthedocs.io/en/latest/

https://github.com/magic-wormhole/magic-wormhole

Check out qaul.net

Yggsrqsil network I2P Freenet https://en.wikipedia.org/wiki/B.A.T.M.A.N. IPFS SSB / Manyver.se / PZP Briar Project Tailscale Syncthing Localsend

There are lots of others, but most either shut down, got turned into scams, or were always scams.

There was one chat app I remember, I think it was called firechat or something. They ended up removing all the P2P features from it and removed all references from their advertising.

I have a strange love in my heart for IPFS. I can't justify it, but it's there. Beautiful atoms... such promise...

Monero - private, permissionless, decentralized, p2p, digital cash system.

Reticulum - cryptography-based networking stack designed to build secure, decentralized, and resilient local or wide-area networks using readily available hardware. It operates independently of traditional internet protocols (like IP), enabling communication under adverse conditions such as high latency and extremely low bandwidth with:

• Forced e2e encryption and forward secrecy
• Initiator anonymity
• Multi-hop and self-configuring routing
• Heterogenous network support
• Decentralized addressing

Basically internet 2.0

Arweave - private, permissionless, decentralized, p2p, permanent data storage/server.

https://positive-intentions.com/

Croc file share, uses a relay to find each other https://github.com/schollz/croc

Session Messenger, uses a tor style server network https://github.com/session-foundation/session-android

• WebDrop - share files with a web browser
• Magic Wormhole - P2P file transfer protocol with many clients

Tox is interesting, though potentially less secure than Briar as they rolled their own encryption and have not been audited (afaik).

there is gnu jami - messenger and video/audio calls