Streaming from phone

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

Wouldn't I?

https://www.newegg.com/p/1W7-00V1-00733?item=9SIC0FCKJN1179&utm_source=google&utm_medium=organic+shopping&utm_campaign=knc-googleadwords-_-cables%20-%20internal%20power%20cables-_-aomoproing-_-9SIC0FCKJN1179&source=region&srsltid=AfmBOopr5ns4cLApzUoZhDMhBwbjKlQzEt7bCKfkx4vaTYNZPdKuNUQt354

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. 

Personally, I think the node sounds better than the WIIM. And it can be slowly upgraded, first by installing A linear, power supply module, and then ultimately by connecting it to an external DAC. and of course, more expensive options abound. Good luck!