How can I listen to DAB+ radio on my iPhone? In my home country we have switched off FM radio and done a full transition to DAB+. 

So, I'm now in the market for a portable dongle (or similar) that will enable me to listen to DAB through my iPhone.

I have come across the POPyourPHONE product that is compatible with Android devices that support OTG and the Lingo iRis for iPhone 4 (1, 2). However, I haven't yet come across a similar device compatible with modern iPhones.

My iPhone has a Lightning connector, but how the dongle connects to my iPhone is not so critical (i.e. it could connect via Bluetooth or even using Apple's Lightning-to-3.5mm adapter). 

The main requirement is that I can use my iPhone to listen to DAB+ radio, preferably with my AirPods. It would be strongly preferable if incoming phone calls were handled OK and that radio could play outside of any dedicated apps.

Can anyone recommend/suggest a product that will meet these needs?
I offer this answer as a possible software solution to meet your needs, although any software solution will require data usage.

I've just checked and TuneIn Radio is available on the Norwegian iOS App Store. For full details refer to https://itunes.apple.com/no/app/tunein-radio/id418987775?mt=8

I've personally been using TuneIn Radio for many years now and have generally been very happy with it. It provides access to over 100,000 radio stations and even offers users the ability to submit station requests in the event a station you want to listen to isn't available.

There is also a Pro version available (obviously at a cost).

NOTE: I am not affiliated in any way with TuneIn Radio.