So much for G+ being a ghost town... I've gained another 30,000 followers in about 2 months and they're not bots as I block spammers and bots immediately
Google+ is showing no signs whatsoever of slowing down as growth numbers are still rising and I'm seeing new people commenting. Looks like we'll be hitting that wall at full speed in April 2019.
I'm hoping Google will leave all posts in read-only mode for a few months so people can see where to find each other.
On the alternatives, I've been trying out the last three months or I've seen by far the biggest growth at MeWe with over 2,000 followers of my Tech Group. The biggest negative for me is that the posts are not public like Twitter. They've said they will still go public, but Groups are really nice to manage and I like the G+ Collections concept. MeWe is already very busy and even some spam bots have appeared (means they're hitting the big time!). However despite their feedback forms, there is little (any?) direct interaction with moderators and owners - support groups seem to run by users self-help, and the replies I've had have twice not even answered my query. Their mobile app is good and their Groups have powerful settings options.
I've seen steady growth on Diaspora/Pluspora and a bit quieter on Mastodon, Hibzilla and Friendica.
I've also joined the brand new (1-month-old) YouMe Social which is interesting... a highly involved owner (ex-G+ user) who has been interacting and already rolled out some new updates and the Android and iOS mobile apps have been sent to their stores for release today. Their posts are already fully public and they're planning RSS feeds too. Groups are there and I'm just waiting for some planned controls to better moderate the groups. But so far so good and I see the concept of being more open here than MeWe so far. MeWe may have an earlier start but YouMe Social is shining quite brightly right now.
Some distinctions between the platforms:
1. Some are centralised like YouMe Social and MeWe - if that site is down or censored then it is offline. Some sites are decentralised and federated like Mastodon, Hubzilla, Diaspora and Friendica - block one and the others still work, post to one and it can be followed everywhere. Nothing stops MeWe and YouMe Social from federating as a single instance of course.
2. Advertising - none of these have ads but some may in future like Youme Social. But they are all committed to privacy though. It is just about being sustainable as there are hosting, development, etc costs and this income does not fall from the sky - Diaspora, for example, asks (and gets) donations. You want newer features quicker, that costs someone's time and money.
3. Groups vs one stream - so MeWe and YouMe Social have well-established groups with central directories so you can find and refine what you see. Versus Mastodon, Diaspora, etc that have one long stream of posts in chronological order. But none of them injects junk, adverts, offers to boost posts, etc. Just nice clean posts to follow.
Out of the above we can expect to see the most changes probably coming from YouMe Social in the coming two months or so.