Delta Chat has the advantage that everyone already has an email address

Combined usage of delta chat and unencrypted mail in the same inbox has been specifically advised against for longer than that.

Delta chat works on FreeBSD.

Delta chat is decentralized but noted down as federated (unlike session even though they have centralized infrastructure without which the app does not work)

Delta chat is compatible with any chatmail messenger (arcane chat, delta touch, parla, etc) yet instead it says it falls back to email (which if they mean unencrypted email is no longer true as delta chat no longer allows unencrypted mail or if they mean encrypted email then the that hasn’t been true for a long time because the email client supporting encrypted email are mostly no longer using open standards)

I could go on but you get the point