I replied in the comment section of steemit's blog about alternative blockchain sites.
Minds - aside from Weku, currently the only one where you don't have to jump through any hoops or wait in order to join and use it.
It's doing its own form of payments and interaction.
The next three are ON the blockchain, every action is IMMUTABLE, which means both PERMANENT and UNCENSORABLE. There are both positives and drawbacks to this.
Memo - uncensorable Twitter.
Matter - in a sense longform of memo. Every action on the BCH blockchain. One big difference between Matter and steemit/Weku is that once you post what you have to say, it's permanent. There is no editing. Same with memo. That's what makes them uncensorable/immutible.
Blockpress - it's... another form of memo? I think memo is better, currently. I mean, you can't even link to the posts, which is what I was about to do, from my blockpress page. Blockchair and Blockchain Explorer don't show text. They show TXs.
Yours - uses the BCH blockchain. Used for writing articles. Currently, you won't be able to join, as they implimented a invite-only protocol... and haven't developed invite links.
Weku - very similar to steemit, but with its own version of payments and incentives.