I still have many different accounts on matrix, lemmy, mastodon, etc. and although you may communicate somehow, it doesn’t work properly.

  • Re: matrix, there’s a lightweight Matrix client that you can embed by basically adding an HTML div and adding a script file to the page. You probably don’t need a full Element embed for basic messaging. In theory Lemmy could add a chat box relatively easily, but then instance admins would probably have to deal with configuring the right security headers and such to make this possible.