Mastodon supports 96 different languages and dialects.

You can choose your interface language, filter your timelines by language, and say which languages you post in. There's also a built-in automatic translation system on some servers (depending on whether your admin has switched it on).

It's important to set your posting language as this is what allows the language filters and automatic translation systems to work.

You can find out how to do all these things at:

➡️ https://fedi.tips/setting-your-language-preferences-on-mastodon-and-filtering-out-posts-in-other-languages