I was skeptical that Delta Chat could work well. It was nevertheless attractive because of its 'self-hosted' nature, so I installed it on my family's devices and set up some accounts. Onboarding needs to be smoother, but it does work. Account detail sync seems flaky, so my family can't see my profile photo, even though I set one.
That said, Delta Chat is amazing. It uses plain old email over IMAP connections to work its magic, and it uses end-to-end encryption to protect the content of messages. Photos work great, and it also supports audio messages, which is a lot of fun. I highly recommend trying it out.