You want a device that converts eARC to optical.  Look on Amazon.  There are several available. 

https://a.co/d/eYY2Mur

I tried the above and it is not working. Do you know of a model that has worked?

thank you.

https://a.co/d/iVshjPY
 

will the above work?

kuntal.

 Never tried one.  Just read about it somewhere.  There is a link in another topic.  Not sure if it works.

https://www.amazon.com/Extractor-Optical-Toslink-Splitter-Converter/dp/B08R5RB41Q

The SONOS optical adapter will send HDMI-ARC audio to RAY. Note that an optical connection is only one-way, it’s not possible for RAY and the TV to have a dialog. This is not a major issue because RAY can be configured to automatically default to TV audio and accept Volume commands from an IR remote.

Edit: I’ve got this backwards. This will not work. Thanks 106rallye.

​@buzz Sonos says this about the optical adapter: “Use this cable to connect your soundbar to your TV's optical audio port.” Are you saying it works the other way around too (form HDMI to optical)?

I think the Sonos adapter is intended for use with a Beam or Arc and a television that lacks HDMI-ARC but has optical out. I don't think it meets the OP's requirements. 

My Sony  TV  hasn't got a dedicated optical out but came with a little adapter that could be used in another output port. Maybe Samsung does the same?

I actually find it hard to believe that there is no optical out on that TV.

No optical port I can see, it does have an eARC port.

Might be worth upgrading to a Beam rather than fiddling adapters.

https://www.samsung.com/us/televisions-home-theater/tvs/crystal-uhd-tvs/55-class-crystal-uhd-du6900-un55du6900fxza/#benefits

Yes - on a quick look on the web it seems it really doesn’t have optical out.  I think the Sony adapter I mentioned must have gone in the component audio port (can’t remember, don’t use it).  But when it’s getting this hard to find something that works I’m inclined to agree with ​@Stanley_4 that you’d be better off going with the flow of tech progress if you can.