Hear, hear. I've been on Hubzilla since long before the big Twitter migrations, I've even got a few channels on (streams) going. And I've got connections all over the Fediverse which goes to show that it's all pretty much connected with one another.
My main channel on Hubzilla (that also posts a lot about the Fediverse):
https://hub.netzgemeinde.eu/channel/jupiter_rowland
My rather slow image outlet channel on (streams):
https://streams.elsmussols.net/channel/jupiter_rowland
Juno's channel on Hubzilla:
https://hub.netzgemeinde.eu/channel/jupiter_rowland
Other OpenSim users who are actually at least somewhat active in the Fediverse include Mal Burns, Thirza Ember, Cheryl Furse, Lone Wolf and a slowly increasing number of Francophone users.
diaspora* is an exception. It still refuses to adopt any other protocol than its own, so within the Fediverse, only Friendica, Hubzilla and Socialhome connect to it. Also, it's withering away rather quickly. Around December 29th, multiple major pods shut down, and according to one stats site, diaspora* lost over half of its users within three days. On Saturday, diasp.org, one of the biggest pods, will be closed.