I have exactly the same issue. But with iOS 13.1.2. iPhone X.
I have reported to Tidal & Naim. I think Apple is perhaps the culprit…?
May I suggest you contact Naim Tidal & Apple support as I did to try escalate the issue.
If you re-run through the 1st time setup wizard and reject the chromecast terms and conditions then the icon won’t appear on the apps home screen. We had to follow Google’s guidelines on this, so it works differently to many other inputs.
At the moment we don’t do a usb disable as that one is a bit of a special input (covers 2 sockets, server mode interaction and device charging). I think it would have to be more a hide so the browse option is hidden. I’ll raise it with the dev team, but is one of the few inputs that is a special case.
I agree with James on this. In fact, of all the inputs I would least want cluttering up the app home page, USB and Chromecast would be the first to go. USB because the content is much better viewed in the server input, and Chromecast because you select it from the third party app, not the Naim app. So these (along with AirPlay) are the inputs I would never need to select.