You don't need to use link shorteners on Mastodon. All links count as 23 characters no matter how long they really are.
Also, links on Mastodon stay in the form you wrote them. This is much better for privacy than Twitter.
Twitter quietly changes all posted links to go via Twitter's domain t.co so they can track people. This doesn't happen on Mastodon or the Fediverse.
You can see this hidden conversion in Twitter by hovering your mouse over a link there, the link appears to show a normal address but Firefox and other browsers will indicate the true t.co address in the bottom left corner of the screen. If you try this same check on Mastodon or the Fediverse, you will see your links stay just as you wrote them.