Sonos sells an HDMI to optical converter - maybe it is supplied with the Arc (as it was with my Beam). If you'd use the converter I think it would work as you expect it. Remember you'd lose the possibility to play sound originating from the TV (apps, cable). If Atmos is important to you, remember Atmos also does not work via optical.

Thank you, yeah I would not want to do that, was hoping for separate optical connection, it was only for the odd disc I have in DTS, sounds like I will have to put up with stereo for some movies.

Trying to come away from disc, don't buy often but do still rent, I may look to rent digitally from Apple or similar service, and just buy the odd disc of a movie I really like providing its in Atmos.

Dump the Sonos system and trade up to LG or Samsung that actually decode DTS. I have the
Oppo-203 too and the only work around I came up with is an HDMI switcher. Run the HDMI outputs from all your devices through the switcher and the optical from the Oppo. I have had Sonos Playbar 5.1 systems fir years and have many DTS only BRD’s. The other choice is get a new OLED tv with eArc on it and go that route.

Can you  explain why eArc would be of help in this case?

Then you are just getting what is decoded from the UHDTV. The Sonos Arc bar now accepts eArc input. If you have an Oppo-203 you are obviously a bit of a videophile along with audiophile. Many BRD’s only had DTS as a choice for surround sound. That was before Dolby Atmos but DTS-X is still better that Atmos since it is more lossless audio. The other choice is upgrade to separates or LG-SN11rg or Samsung HW-Q950t systems. I have Oppo-203, LG-OLED65CX and still have Sonos Playbars. I am waiting for more information on the LG and Samsung items and even if I wanted to Sonos ArcBar, I couldn't get one now. I am waiting a bit to see if Sonos steps up to decode DTS, (I doubt it), or just order 1 Sonos Arc for the bedroom with no UDP, (universal disc player), and LG or Samsung for the media room. If my wifey will let me, I my go separates for media room.

Update

I’m loving the Sonos ARC and recently added the SUB, for DTS blurays Im actually not fussed if I view them with stereo sound, and I can also use my xbox to transcode them to DD 5.1 if I wish.

I actually stream a lot of stuff now so DTS is not as big issue as I thought it would be for me.

You, and your reasoning iswhat Sonos is relying on to sell more items. No offense meant in nay way. There are those of us, that strive for the most accurate audio when we choose to view discs that have DTS. Streaming is the much more common solution so it would be great if those what would like to pay for DTS decoding with and optional firmware update, many of us would gladly pay for that option. We hav been dedicated to and enjoy our Sonos systems. They could be truly at the top, if they would decode DTS and if we choose to add or already have rears, the side firing speakers in the ArcBar would act as mid-surrounds and decode 7.1.2. Even better, bring Play5’s or One’s with upward firing drivers so Sonos could do 7.1.4 and beat out LG and Samsung. Total cost is about the same so price isn't an issue

+1 I’d certainly pay to enable DTS as an optional license upgrade.

Personally don’t see the point in Sonos wasting time adding DTS, fix other things and add LPCM.

DTS seems to be getting less traction, the ARC is has no inputs and is aimed at the streaming market that is 99% dolby.

Even TVs like the LG CX don’t support DTS.

Lol and i just realised Im replying to my own thread! , just shows that since owning the ARC, Ive not been bothered about lack of DTS.