You can't. The line in is disabled when used as surround due to the special 1 way connection between the Five and Arc.

Thanks for the reply unfortunately this is not fair… basically this is a key feature in Sonos FIVE that is really frustrating to lose it when grouping to ARC. Hopefully somehow Sonos studies how to make it available.

Fair's got nothing to do with it, it is what it is.  Surrounds are configured as a slave to  the soundbar over a one way private 5 GHz link and thus cannot broadcast the line in back to the soundbar.  My advice, get 2 One SLs for surrounds, Fives are overkill.  Use the Fives as standalone stereo speakers.

As surrounds they are, but music playback they are awesome all together. I’m wondering what option will be best. Your suggestion or getting a PORT (not sure if this will work with current setup, my guess is yes)

Port would work fine.

Finally cheapest solution I found to this ISSUE/CONCERN was to connect my turntable to my TV AUX line in using a $3.0 USD RCA to 3.5mm TRRS cable.

Which requires the TV set to be on? Or does your TV pass through without power?

It does, I just plugged in my turntable with build in amp on directly to TV line in using cable I mentioned above and that’s it (no additional power added). TV pass thru signal to ARC (connected using TV e-arc port). It sounds perfect, no issues. Great thing is that now I can use tv control to up/down volume without app.