It seems like with the recent wave of news about social media migrations (reddit, facebook, twitter, twitch, tiktok), people are hopefully starting to get more and more warmed up to the idea of protocolization of their social data.
But most of the projects doing it are still just too immature. Solid, Perkeep, Blockstack, etc. just seem like vaporware.
Seems like the only serious projects in use are Matrix, Urbit, and ActivityPub/Mastodon. But I haven't checked in with the decentralization scene in a while.
To add to your list, there is also Secure Scuttlebutt  which has had a decent userbase over the past few years, and Planetary  which is a funded iOS client for it.
I think in general they all suffer from the chicken-egg problem and will need some reason for enough people to switch to be able to build a userbase. There isn't really any "novel hook" like tiktok, twitter, whatsapp, instagram, snapchat, etc have had in the past.
So I'll write my app outside of SSB, hopefully in a way that's mostly compatible, and possibly with future integration.
I may also toy with an SSB-like protocol myself, as the fundamentals of SSB is a work of art imo. I really enjoy what Gossip brings to the table, and how SSB focuses on human->human relationship to bring P2P to the table.
The same thing happened with remoteStorage. There's initially a flurry of proof-of-concept apps, but no commercial quality killer apps to attract daily users.
AFAIK the only cloud storage protocol really used for app development is Google Drive. GDrive got successful by making a great cloud storage solution first, then once everyone had one app developers started making apps for it.