Do you like Mastodon, but wish there was a privacy option to only post on your home instance without federating?
There's a fork of Mastodon for that called Hometown:
https://github.com/hometown-fork/hometown
You can still post normal posts that federate, but Hometown also lets you post non-federating posts if you prefer.
It also has other differences such as rendering full articles from Write Freely (and other federated blogging services).
It's by @darius