All of the state of the art end-to-end encryption in products I know of is free software.
Much more difficult to verify these claims otherwise.
Furthermore, the app privacy label on the App Store claims that this service collects your contacts. So much for privacy, then.
Any conversation that includes OpenAI's GPT also necessarily can't be "completely private" or end to end encrypted as the service must have a plaintext of the messages to proxy them (in cleartext from their view) to their OpenAI APIs. It also then, you know, uploads your messages to OpenAI.
What's the point of e2ee messaging if the service provider and OpenAI can read it all the moment you loop in the headline feature (GPT in your groupchat)?
Ultimately, threaded e2ee groupchat is a feature (ideally a feature added to Signal), not an app/company.