Privacy

To be honest, I'm only using Matrix for the bridges into every other service, so I can talk to people on messenger, signal, telegram, discord and whatsapp through a single app, the Matrix client, so I at least don't have spyware on my phone, even though they'll get my messages. And E2E encryption doesn't apply in that case, so I never had to deal with it.

With self-hosted solution, your main advantage is that you can simply create the accounts on the server side, and don't need any verification. After the first login, it usually asks for every new device, that you have to confirm the session on a device that's already confirmed, but I never had issues with that.

But I don't have experience with actuall Matrix to Matrix communication, I just used the bridges. Haven't tried DeltaChat yet, but tbh I've just given up convincing people to switch and am glad I can at least have the bridges working, so I never have to login or use any apps or websites of FB/Discord/whatever.