I've tried getting a Raspberry Pi and following some guides to turn it into an internet radio broadcaster that I can then pipe into Sonos, but the audio quality was always atrocious and the case that came with my Pi kit has a fan that is super loud.
I could get a Sonos Port for 700 AUD and do it the official way... but my record player is only like 300 AUD so it doesn't seem worth it. Here's hoping I can find a cheap used one.
Sonos needs to add an analog audio in port on more of their devices.