Cypherpunk Paolo Ardoino is building infrastructure that allows building decentralized apps that don't require servers to work (

Holepunch

The Peer to Peer Company

). Their first app using this tech is a messenger called keet.io It's not open source yet, but they plan to release the code to the public once fundaments are solid. If it works well, it will allow to build any type of decentralized apps on top of it and with proposed structure (no servers required) economically, imho, it's more reliable than nostr.