So, first things first. You need to set your expectations. For example, no matter where you go, you won’t find all your friends, followers, or social media leaders. While it appears Mastodon is attracting the most people to date, popular figures are scattering all over the social internet. For example, Ryan Reynolds, aka Marvel’s Deadpool, is now making his virtual home on the old-school Tumblr network.
Each network’s user interface and features differ from one another. For instance, it’s relatively easy to find people on Twitter, but it can be quite difficult on Mastodon or Diaspora. That’s because they run on independent servers, aka pods or instances. Twitter, and most other social networks, run on centralized cloud services. 
Each network also has its own rules. Some are much more strict than Twitter. Counter.Social, for example, doesn’t allow ads, fake news, trolls, or even access if you live in a country known for hosting bots (such as China, Iran, or Russia).  Generally, other social networks are not centered on short, pithy messages. While Counter.Social limits messages to 500 characters, most will let you write for as long as you like. Hashtags, which can be very useful on Twitter, don’t get as much support on any of the other networks. 
Another problem with many of them is that they’re focused on small communities with a single interest. Twitter enables you to follow different people from many areas. For example, while I care a lot about Linux and open-source software, I also care about science fiction, history, and musical theater. On Twitter, I can follow thought leaders in all those areas. On the other networks? Not so much. 
With all that in mind, here’s my brief survey of the best Twitter replacements.

Strict rules against trolls and fake newsPosts are displayed in chronological orderNo commercial users or advertisingRelies on donations

This cloud-based social network is known for its friendliness and its strict rules against trolls and fake news. But that won’t be to everyone’s taste.  Posts are displayed in chronological order. The result is much cleaner and more enjoyable message streams. Its desktop interface looks much like TweetDeck. That is, it gives you multiple ways to display messages in columns. So, for example, you can have one for friends, one for notifications, one for all messages (aka the firehose), one for fellow Linux fans, and so on.  Counter.Social also doesn’t have commercial users or advertising. To keep the lights on, the service’s founder, The Jester, a hacker and activist, relies on donations. For $4.99 a month, donors get a Pro account. With this, they get a selection of embedded news channels, such as MSNBC, and the ability to send self-destructing messages.

Open-source-based social network No central site, organization, or even softwareThere are pods run by individuals on their own serverAll pods are joined together in the Fediverse

Diaspora (or, technically, Diaspora*) is an open-source-based social network of social networks. Each “pod” is run by an individual on his or her own server. These are all joined together in what’s called the Fediverse. Unlike Twitter, there’s no central site, organization, or even software. You simply hunt down a diaspora pod that suits you, join it, and off you go.  In my case, I belong to Glass Wings, which tends to have people involved in technology and art. Unfortunately, it’s not admitting new users at this time. Can’t find one that suits you? Then start your own pod with your own interests and rules.  Regardless of the platform, you won’t see advertisements or algorithms that decide what messages you’ll see. Instead, it consists of multiple, small cozy communities of like-minded people. Once you’ve joined, you can connect and follow people on other pods. Finding them on the Fediverse, however, can be difficult. You must have that person’s specific ID to track them down.  The interface, which to some may be more like Facebook than Twitter, can also be difficult to navigate. For example, you can’t edit messages once they’ve been posted – not that you can do that on Twitter either.  Like most social networks, when you get right down to it, the real value you get from it is from the people you follow and befriend on it. For me, Diaspora has an agreeable mix of like-minded folks, so I’m willing to put up with the interface.

The Fediverse social media network most people knowOpen-source-based social network of small communitiesIt does have useful tools for migrating from TwitterMastodon’s interface is on the rough side

Mastodon is the Fediverse social media network most people know. It’s also certainly the most popular. The open-source group behind it tweeted – oh, the irony! – that: “Over 1 million people have joined Mastodon since Oct. 27. Between that and those who returned to their old accounts, the number of active users has risen to over 1.6 million today, which, for context, is over three times what it was just about two weeks ago!” Also: Ditching Twitter? How to get started with Mastodon Like Diaspora, Mastodon is an open-source based social network of small communities. It, too, is part of the Fediverse, with both its advantages and disadvantages.  Because it’s more popular than Diaspora, it does have useful tools for migrating from Twitter. For example, you can use debirdify and Fedifinder to search your Twitter account for the accounts you follow there and try to find matches for them in the Fediverse. This makes it much easier to catch up with people you’ve been following on Twitter. Mastodon feel is more remindful of Twitter than Diaspora’s Facebook-like look and feel. For example, when you get an account on one node or another and start following people, you’ll see a scrolling feed of posts from their accounts. That said, Mastodon’s interface is on the rough side. I like Mastodon, but I’m unsure how far its initial wave of popularity as Twitter staggers about can carry it.  Read the review: Mastodon isn’t Twitter but it’s glorious

More like an early social network such as MySpaceMore image-oriented than Twitter Colorful, simple interface that supports micro-bloggingIt has advertising, but you can pay to shut them down

Unlike the other social networks, which many of you have never heard of until recently, Tumblr has been with us for almost as long as Twitter. With its colorful, simple interface that supports micro-blogging, Tumblr reminds me more of early social networks such as MySpace than their more modern descendants. Leaving its looks aside, Tumblr is easy and fun to use.  It’s also more image-oriented than Twitter. But it’s not bound to images the way Pinterest and the untrustworthy Instagram are. Tumblr is also more blog-post-oriented. It can and does act as a discussion network too – but it’s not as conversation-oriented as the others.  You can also share people’s posts and begin your own conversation.  Unlike all the other social networks I’ve covered, Tumblr is a commercial business. To pay its bills, Tumblr has advertising. However, you can shut these down by paying $4.99 a month or $39.99 a year. The ones I chose to look at here struck me as both good and “Twitter-like.”  For example, if you wanted a replacement for Facebook, I’d point you instead to MeWe, but it’s in no way a Twitter replacement. I also decided to skip the beta social networks. These potential Twitter replacements include Cohost and Twitter’s founder Jack Dorsey’s own Bluesky. Who knows? Maybe Google will finally get off the stick and bring back my own all-time favorite social network Google+! But, in every case, they’re either not broadly available or too new to say anything concrete about. Maybe they’ll be great. Stay tuned in a few months when they’re more mature for my take on them. An excellent way of thinking about these networks is email. No single group runs email. It’s a system of common protocols that enables people around the world to connect with each other over different email servers. Some, like Gmail or Outlook, have millions of users, while others have only one user. Regardless, they let you talk to each other. The same is true of the networks on the Fediverse. That also means each Fediverse site can have its own rules and software. This gives them independence, but it also means they’re fragile. If someone wants to close down their Mastodon or Diaspora instance, your account goes down with them.  So, yes, I guess, if you’re an optimist or a true blue-check Musk fan, you can hope Twitter will survive his technical, staffing, and policy blunders. Me? I’m waiting for the crash and for someone else to clean up the mess. Something will, however, emerge. For all that Twitter under Musk is a mess, there’s still a strong audience for a short text, news-oriented discussion social network. Whether that will be Twitter, one of the other social networks, or a new one that doesn’t even have a name yet remains to be seen.