Yes, it is now available to all Mastodon servers. If your server is running the service, you will see a “Translate” link underneath a post in a different language. If you don’t see these links, ask your server admin about it.
The feature relies on knowing which language you speak, so make sure your account’s language preferences are set correctly, as this will allow the system to automatically suggest translations for you. If you have the incorrect language set on a post, it may confuse the translation system.
This feature is currently only on the website interface and also on the excellent third party app Fedilab ⧉.
The built-in translation uses open source translation provider LibreTranslate ⧉.