Offline Translator https://f-droid.org/packages/dev.davidv.translator

I use Kagi translate, I don't use translators often so I cannot really share my experience. In times I did use it it had helped me perfectly fine

If it's purely a degoogling question, deepl.com translation is very good, though idk how private it is. For privacy, the built-in Firefox translation is crappy but usable if you're just trying to get meanings of things. IDK if it's available (or easy to separate) as an outside-of-browser CLI utility.

Google translate in Tor, no javascript:

http://xxtbwyb5z5bdvy2f6l2yquu5qilgkjeewno4qfknvb3lkg3nmoklitid.onion/

Alternatives, yes... GOOD alternatives, no. The rest of the industry is 5 to 10 years behind Google as they leveraged their services to train AI Translation before others and have all the refined data to go with that for many more languages than even AI Competition. The one hope and genuine AI Trasheap is that competitors can catch up faster.

i personally use deepL because its very very accurate, but for pure privacy you could selfhost libretranslate or use the many public servers.

Google translate is pretty awful. I use deepL, but idk if it's not privacy friendly. It's better and it's at least not Google though.

Full sentence translators? Only ones that come to mind are LibreTranslate, plus if you'd like to try, the instance from Mastodon.Uno's group since the LibreTranslate dev team's official instance requires an API key. Also maybe local LLMs if you trust they won't go rogue and connect to open wifis like LG TVs do, or if you can ensure they won't escape containment.

Furthermore, if you just need to translate individual words or some times smaller expressions, there's disc-based translators and dictionaries though they usually require older systems, maybe Google Play ones (specially paid ones) if you keep them in an offline VM with Vanilla Android, QuickDic on F-Droid, etc. For CD and offline dictionaries, I collect them, so I can also comment on specific ones or on specific language combos.

some m8s use libtrans. I trynot to, as a polygot, I can read the subtleties it fails at.