Copy the music onto an NAS device? 

I can’t remember if that Connect has a line-in, but if so:

Lightning to 3.5mm jack adapter? 

Bluetooth receiver for the Connect? 
 

Edited to add:

RCA connections, so lightning to RCA cable. 

I assume you have speakers connected to a Connect:Amp.

The Connect:Amp does not support AirPlay 2 directly. However if you have a compatible Sonos speaker that does support AirPlay 2 you can start AirPlay 2 from your iPhone to that speaker then group the Connect:Amp to it. 

Click the link for compatible Sonos AirPlay speakers:

https://support.sonos.com/en-us/article/stream-airplay-audio-to-sonos

Note: This is not possible with a Connect:Amp used to drive surround speakers.