The concept of federated alternatives is that each participant would only need to host only a tiny part of the whole set. See Fediverse (Mastodon…), PixelFed or PeerTube. It’s completely greenfield, as nobody has dared to address the problem like that in the past.
By the way, I’ve gathered all related (centralized) services and pages to a new category for a better overview.
https://wiki.openstreetmap.org/wiki/Street-level_imagery_services