Pro-Ject Debut Carbon Evo Turntable with Sonos Arc SL and 2 Sonos One SLs

Pools-3015: Thank you very much for your reply, your information is very helpful to me. I appreciate your effort to respond to my question.

I have the same turntable and I use a Port grouped with the Arc, 2 Era 300’s and a Sub. I named the Port “Turntable” and select it with Line-in as the source. Between the Port and the turntable, I use a Phono Box S2 pre amp. 

Pianomstr: Thank you for taking the time to respond and provide me key information about how to set up the Port with pre-amp. Much appreciated!

Probably...too late to return the Pro-Ject Debut Carbon Evo Turntable....

However, for $799 (USD) you might have considered the Sonos Editon of the same turntable that includes a pre-amp and upgraded Ortofon 2M Red cartridge as well as a Non-resonant acrylic platter.*

Click the links 

• https://www.sonos.com/en-us/shop/pro-ject-debut-carbon-esprit-turntable-walnut
• https://www.sonos.com/en-us/shop/pro-ject-debut-carbon-esprit-turntable-black

* Assumes the price of the TT you purchased was $599 plus $100 to $199 for a Pre-amp

And just another advice… you don’t have to „group“ the home theater room (including soundbar, sub, rears) with the room (including the device with line in connection), if audio just shall play on the home theater setup. 
You can use the ht room and just select the other rooms line in as source for the ht setup. Or even more comfortable go to line in settings of the line in supporting device, turn autoplay option on and select the home theater room as destination. 
This way there is a more stable connection on the network than with grouping. You will just need a group, if you like line in audio to be played on several rooms in sync. 

.: Thank you everyone for your help and advice. I fiddled around with the device(s), rebooted my router, and finally, at long last, music came out of the speakers when the needle hit the vinyl!

Now, crazy as it sounds, I can’t determine how to control the volume. I've moved the Volume Limit on the Sonos app up and down to no avail. It returns to 100% for maximum allowed volume. On the preceding screen it reads, “Volume Limit Off.” Line-Out Level is set to “variable.”  Thoughts on what I’m doing wrong or what I am missing here?

.: Update: Not sure what I did, exactly, but I have sound from the turntable through my Sonos Arc and One speakers, and also found a setting to control the volume coming from the Port.

So for the moment, all is well. Again, thank you to everyone who responded with help and advice.

@Podbay 

I suppose you first tried to adjust volume of the Port room… but you have to select the home theater room as the active room and control its volume. 
And if you select your home theater room as destination for Ports line in autoplay, you there can also set a standard volume level for starting autoplay. 

Hello, Schlumpf. Thank you for the additional guidance. I think I’ve determined how to switch sound between my TV system and the Pro-Ject system. And I’ve set the autoplay for the turntable/Port to a lower volume. Again, much appreciated.