Replying to myself, if there was an update to the book, I think it would be great if you could extend Part IV with guest-written chapters on how to connect it to other frontends such as Flutter, iOS and Javascript frameworks other than React.
For example, perhaps Paul Hollyer who maintains the elm-phoenix-websocket library, would be up for writing an Elm chapter. The fact that he recently released v4 was another reason I picked up your book again.
It’s not that these additional chapters would necessarily add knowledge on using Phoenix for real-time that isn’t already in your book, but they may introduce experiences and strategies more suited to their specific domains.
Anyway. Thanks again for the book.