Maybe there is more development going on in individual projects? ActivityPods which combines ActivityPub accounts with Solid Pods for identity management — and AFAICT it was last updated two days ago.
I have to say I'm still not clear on exactly what and how Berners-Lee & co intend us to use Solid. Presumably the pod providers are more reliable than Google or Meta, but they're still unknown third parties to me? Should we self host our pods? That's only a power outage away from becoming a real nightmare.