

They are not supposed to be able to and well designed e2ee services can’t be. That’s the whole point of e2ee.
You’re using their client. You get a fresh copy every time it changes. Of course you are vulnerable to a MITM attack, if they chose to attempt one.
In the 80s I went to a public event featuring the California Joy Stick; “Joy” referring to the brand of dish soap. There’s probably a more common name for it. It’s a device made of a large fabric loop on a stick with a nut for holding the loop open. You dip it in a solution of water, dish soap, and glycerine, and then open the loop to the breeze or walk with it. You can create bubbles tens of metres long, and wide and tall enough for a person to stand inside. I’m surprised it isn’t still a thing people do, you could easily make one.
There was a bubble making competition. Most of the competitors seemed to be quite casual, but most of them found it fairly easy to be competitive.