@oilyfish
I thought URL shortening was built into the #Mastodon server. If you enter an URL, you should see that the number of characters deducted from your allowance is less than the number of characters in the URL.
I can't suggest an URL shortener but I will say that #tinyurl is the worst of them b/c of the #netneutrality abuse of #CloudFlare. All 3rd party URL shorteners (e.g. bit.ly) abuse #privacy to some extent (it's how they make money).