Since it’s an ARC signal that the Sonos Arc is depending on, it needs to be a relatively “new” / capable length of cable. I don’t have much experience here, but going with a newer HDMI 2.0 or above spec cable, likely high speed, and probably no longer than 30 feet, would get you the experience you’re looking for. Longer than that and I’d be worried about signal attenuation, but I’ve seen lots of video streams working at lengths of up to 50 or more feet. 

Note that the Samsung Frame has had a significant number of complaints about the implementation of HDMI not working well with Sonos. Do a search for “Frame” and I suspect you’ll find several threads about it. 

I wouldn’t refer to your setup as high end, or that Sonos can’t handle it.  You need to have proper HDMI cable to use HDMI-ARC/eARC over long distances, rather than whatever you had laying around or would could be had for cheap.  This would be the case with any audio equipment that used HDM-ARC/eARC and any price point.

I’ve used  this cable  with a Sonos amp a couple times, longer than 20 feet.  No issues.  I don’t need a long cable for my Sonos Arc.  I honestly would go with an HDMI 2.1 cable if I were buying today though.  A search for “hdmi 2.1 cable 15 ft” should give you plenty of options.  

I’ll repeat here what I’ve expressed many other times, and I’m sure @melvimbe is tired of hearing it….it’s unfortunate that so many manufacturers of HDMI cables do a poor job of labeling which version of HDMI it supports. It’s relatively easy to get one designed for an older version of HDMI (1.0 to 1.4, for instance), and take the assumption that it works in the same way as a newer version. Often there’s no way to tell. One of the things I try to do is look at the definition stamped on the cable, but there are manufacturers that don’t do that. So I’ve frequently replaced an ‘older’ cable that did fine for carrying just video with a newer high speed cable, which deals with ARC more efficiently (or at all).

2.1 compliance would likely be an excellent cable to use in this case, but I’d still caution about Samsung’s implementation of ARC, particularly on the Frame, as being potentially problematic. Since I don’t own one, I don’t know offhand if they’ve rolled out a firmware update to the device that fixes the previous issues…..but then again, the volume of complaints has gone down, so it might certainly be possible that they ‘fixed’ it. 

Never

I find that I tend to keep a large box of spare hdmi cables handy, but when I actually need one, I tend to just buy new without even trying my old ones.  

Yea, that’s possible, but since OP said that it worked using the HDMI cable provided by Sonos, it makes sense that the longer cable is the issue.

Thanks for the Postta recommendation, I’ll give that a try @melvimbe. Thanks for the context on the Frame issues @Airgetlam.