In Delta chat on android I currently don’t have previews of shared links. Can this be accomplished with Webxcd app? Or else, is there another Chatmail client that has it? Or would it need server-side support?
No, it is not possible with sandboxed webxdc apps as of now. It would be possible with a different, “client xdc” or “system xdc” extension that could plug into the interface. It is already possible with a bot, however.