The best alternatives to Unbabel are GoSquared, Boomerang, and Text/Turner. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Unbabel?
AssemblyAI— Multilingual Speech-to-Text API with superhuman accuracy
Boomerang is an iOS app that allows you to translate your text and see that translated back. It leverages Google Translate to provide translations between over 100 languages.
RTranslator is an (almost) open-source, free, and offline real-time translation app for Android. The app uses OpenAI's Whisper for speech recognition and Meta's NLLB for translation, it has 3 modes: A classic text translation mode. Conversation mode: Where you connect to one or more devices that have RTranslator to have a real-time translated conversation with other people (works best with Bluetooth headphones). WalkieTalkie: Where you can translate a conversation with a single device.