I was looking for this too. shared one that was client side encrypted. No realtime chat though. SecuriNote.com

Does it matter? They'll surely wouldn't implement a local/client-first E2E encryption, so in the end they'll be holding the keys anyways.

If you want something private, don't put it on other people's platforms, it's very simple.

No, it is not. But that's high on the list of things we're focusing on.