This is probably a good read for you:
https://en.community.sonos.com/music-services-and-sources-228994/using-a-turntable-with-sonos-6769426
But on to the more esoteric. Generally speaking, a turntable or pre-amp will have RCA output jacks. You could conceivably get a device that takes stereo input from RCA jacks to an optical output that you could connect directly to the PLAYBAR. Now, if you use your PLAYBAR to watch TV, I wouldn't recommend this, as switching the optical cable from TV to Pre-amp/turntable might be too much handling, and the plastic connector might become deformed.
Bruce