Federated infrastructure but user sovereignty: a “third way” between federated and P2P networks.
But we don’t need to go the whole P2P hog to get robust user sovereignty. Cryptography lets us separate who stores and routes data from who truly owns it. We can combine the easier infrastructure design of a federated protocol with the full decentralized security of a peer-to-peer protocol.
If it makes you feel better I think the question of “where that happens” isn’t a a solved one really! Some examples of answers though are on the blockchain (essentially paying to be stored as part of the consensus mechanism’s data), IPFS (either volunteer or personally hosted off of it, or through a paid service to ensure it’s hosted somewhere), or stored locally by the user either manually, as part of a hardware token, or in browser cache.