http://lainyubrp2aabmxhepbttfdbl53dct2inqifs42buvpf6w44uiitbeqd.onion/blog/matrix.html
I would even say that the whole point of using matrix is it's openness and possibility to store your messages on your server or over the federation, on homeservers you trust. Not in cloud, this way you could just use something like telegram. And end-to-end encryption, of course, but I'll look into it later. Implementations... It's bad.