No.  The source will entail a DAC to ADC conversion from the DAC to the Line-In, and all “quality” from playing the so called hi-res audio will be down sampled to 24/44.  The highest quality will be reached by playing Apple Music directly from the Sonos app.  That will entail no conversion and will stream at the highest quality Sonos can handle.

Thanks for your response. To confirm the best quality that the Era 100 can handle is 24/48 via airplay 2, Sonos app and line in.

I’m not sure what Airplay 2 uses.  But yes, the top resolution for music on Sonos is 24/48.  Which makes sense, because all a higher sample rate gives is the ability to capture frequencies above the threshold of human hearing,.  In general, the idea that a greater sampling frequency gives better sound is audiophile snake oil.  However there are some benefits to the remastering that is sometimes done to produce a high definition version.  

Thanks. I have the DAC and iPad which I play with my old amp and it sounds really great. Wanted to retire that configuration and replace with Era 100. I bought a Sonos line in adapter thinking that airplay 2 quality will not be 24/48. Looks like I wasted some money, unless I can return it to Sonos and successfully get a refund