You need to convert the TV output to analog then. Or get a new receiver with a DAC for the TV and RCA inputs for the turntable. What you're asking for doesn't exist. Sound has to be converted to analog to play through speakers. So you need to figure that out. Get a DAC. Something like this will do this.
https://www.amazon.com/PROZOR-Digital-Converter-Optical-Toslink/dp/B00KNNSKV0

Once this is figured out, you can get a passive stereo preamp like Schiit Sys or possibly a switch like this. Becare, this one should work. But others may add hum.
https://soundapproach.com/rek-o-kut-low-noise-stereo-phono-aux-switch.html

If you just want to split the sound without a switch you could try a Y-connector. But this may cause problems like humming.
https://www.amazon.com/Splitter-Adapter-RFAdapter-Subwoofer-Speaker/dp/B08ZSS6GL4