Streaming from phone

I think you would be better off using your phone with Wi-Fi.  The sound quality will be better. Even if the Wi-Fi is not connected to the Internet, your phone would be… And you can feed it music via Qobuz connect.  

I would still require a intermediate piece between phone and pre amp

Wouldn't I?

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You need something like this if not using a streamer with an iPhone .    USB C to RCA if using a Samsung. 

I would get something like a WiiM or Node and use the phone as a wireless Hotspot. 

Remember that Bluetooth is a lossy format -- like MP3. While lots of people are fine with Bluetooth, it does reduce sound quality. 

@peter_s is correct, you can set up a wireless network at the cottage without being connected to the internet. You will just need a streamer with Wi-Fi so that your phone can send lossless music to it across the network.