It's got slightly different takes on many issues, but hopefully seeing a different perspective will give you a fuller understanding of how Mastodon works.
PixelFed uses the same federation protocol as Mastodon, which means Mastodon users can follow people on PixelFed and vice versa. You can try following a PixelFed account right now such as @Iancylkowski or @JoseMel or @connyduck
You can use PixelFed through a web browser, and there are also free open Android apps like @PixelDroid and FediLab (@apps).
As it uses the ActivityPub protocol, you can follow and interact with accounts on Mastodon etc from Friendica, and vice versa.
You can also follow RSS feeds as if they were Fediverse accounts, and when an RSS item is published on that feed it will appear in your timeline as if it's a Fediverse post.
You can write very long posts on Friendica, you don't have to worry about character limits.
You can use Friendica accounts through the FediLab app, available on @fdroidorg and Google Play.
You can follow the latest news about Friendica on its official blog at @news
There's an alternative version of Mastodon called "Mastodon Glitch Edition" (aka "glitch-soc" or just "Glitch"). Glitch is totally compatible with normal Mastodon, but adds experimental new features.
For example, Glitch instances let the admin alter the character limit, allow local posting, text formatting and lots of other stuff.
Many features in Glitch have eventually made their way into normal Mastodon after proving themselves stable and useful.
If you run your own Mastodon instance you can switch to Glitch, and switch back again if you don't like it.
(You may be wondering how this post is so long? It's because FediTips is on an instance that uses Glitch, and the instance character limit has been extended to 1000.)
Do you have a WordPress blog? Did you know you can connect it to the Fediverse?
✅ There's a WordPress plugin which lets people on Mastodon (and the rest of the Fediverse) follow, share and comment on your blog. It's called ActivityPub For Wordpress and you can get it from here: https://wordpress.org/plugins/activitypub
The desktop version of Mastodon has two different interfaces: a single column Twitter-style one, and a multicolumn Tweetdeck-style one.
✅ To switch between Mastodon's desktop interfaces, go to Preferences > Appearance > Enable Advanced Web Interface. Selecting it activates multicolumn, unselecting it activates single column.
Multicolumn lets you add lots of additional columns, which may be handy for desktops on very wide monitors.