Facebook messenger tries to marry end to end encryption with multi-device access and it's a horrible mess with some messages not being delivered to some devices for hours , days or ever.

I absolutely want OpenAI to keep all of my chats and I absolutely don't want them to share them ( voluntarily or by force) with any private agent.

I have exactly the same expectation of any document or communication platform. It's been long established as accepted compomise between security and convenience.