I use Deepl

• Lingva is a private frontend for Google translate
• LibreTranslate is an independent, free, libre, open-source translation solution
• Translate You is an Android app that allows you to connect to various translation APIs, including Lingva and LibreTranslate
• Firefox Translate allows you to translate websites when using Firefox or LibreWolf

LibreTranslate is an option if you're looking for something open source.

Translate You features LibreTranslate, Lingva, DeepL, MyMemory, Reverso, and SimplyTranslate.
While I can't speak for any of them, I think that all of those should be safe being that Translate You is FOSS, and their idealogy is "No Ads, no trackers, just You"

Firefox translate seems pretty good

Lingva is an alternative frontend for google translate if you're open to that, this is one instance.

At the moment, DeepL is the only option for accurate and convenient language translation.

I wish there were others, but everything else sucks.

The SimplyTranslate front end has many languages, translate engines selectable: Google | DeepL (Testing) | ICIBA | Reverso | LibreTranslate. Some instances are Tor-friendly, even onion. The project page seems to be https://codeberg.org/SimpleWeb/SimplyTranslate

Refusing to use Google is just common sense. LibreTranslate itself is decent (at least not Google), except a website hosting it may have some opaque JS or Google things (Font, Analytics, TagManagers, etc.)

Either way, translation can’t be super-private in general. For example, if you use it to write a private message or love letter in a foreign language… even including real names and physical addresses…

Also, metadata like “a Danish-speaker is reading this German text about X” can’t be hidden, and if the language pair is uncommon and/or if text to be translated is specialized (not generic), the engine provider may easily guess “this request and that request yesterday may be from the same user”, etc. if they want to. A sufficiently powerful “attacker” might de-anonymize you, helped by other info about you, already gathered. In practice, maybe not a big concern, if you’re just translating generic, non-sensitive text, not showing your real IP, and clearing cookies frequently.

I use Translate You on Graphene. Works great!

Microsoft translator exists. But is is also a MAGMA company.