Just done a System update on my NOW 4K Smart box and found under the Apps Store section that the Discovery + App is available.
If you can't find it under Apps Store use the search Apps option in the Apps Store section.
I don't subscribe to Discovery + so I can't check the App out.
Have to admit I’m totally shocked at this, especially considering how long the app has been out for and it seemed like no new apps would be added to NOW devices. Which begs the question, what about Paramount+?