You need a phono pre-amp and a Sonos device with a line in, of which the Five is a good choice if you don't yet own a Sonos device.

The receiver has a phono preamp so you plug the turntable into the phono input on the receiver.  You then run a cable from the tape output on the receiver to the line input on the Sonos Five speaker.  If you want to get rid of the receiver, then you need a phono preamp for the turntable that would output to the Sonos 5 input.

Try what John suggests, that should work and allow you to keep what is a quality receiver if it is in good working condition. If the receiver is still too much footprint and you must let it go, then get a phone pre amp to replace it.

If the receiver has a working radio, the above scheme will allow you to also play it through Sonos speakers.

The Five is actually the only Sonos speaker with a line-in, so that’s the one you want. You’ll need a male stereo RCA to 3.5mm male stereo jack to make the connection, whether you use your existing receiver or a new phono pre-amp.

I’d keep the receiver myself and use that for your turntable, but yes, any modern phono pre-amp will work with your vintage turntable if you decide to simplify the setup.

So would I, but that is the kind of decision that will mostly fall on either side of the gender divide!

These are super super helpful comments. We will keep the receiver per your recommendations and get the Five. We actually did some repairs on both components when we received them a few years ago so they are in good shape. I greatly appreciate the detailed advice!  You are all very kind!

If you have access to the skillsets needed to repair this kit, keeping it is a good idea. Sound quality from the receiver is as good as it gets even today from modern kit, and, unlike modern kit, with service support it is built to last for decades.

Just curious; why are you not considering getting a pair of modern passive speakers of modest size for the receiver instead of one Five? Sound quality will be better than from one Five for about the same price. There is a one time effort of running speaker cables, that’s all.

If you can post a photo of the rear panel of the receiver, someone here will be able to tell you how you can use it to also play the same music to Sonos speakers in other parts of the house, if desired.

Here is the back panel. The reason we want a five is that we are creating a very calm, zen, minimalist look and want to multi-use our audio system - mostly we will likely use Spotify, radio, occasionally LPs, maybe TV. So it seems like Sonos is more multi-functional. 

Connect your turntable to the Phono Mag 1 jacks and ground nut as usual. Use a cable like this to connect the Five to the Tape A Rec jacks. Make sure you have Phono selected on the front of the receiver and use the Sonos app to select Line-In as your source.