Sonos isn’t the determining factor in this decision, other than the remote needs to be IR if you’re using a PLAYBAR or PLAYBASE. The Sonos software can be “trained” in the controller to match any signals sent across IR. Other home theater products use CEC to get the command across the ARC from the TV set.  Any remote that can connect to the Sonos system (not that I’m particularly aware of any, I use my iPad and iPhone) would work.

Thanks. I understand all the technical needs. But, that knowledge didn’t resolve my issues with Harmony. So, since I am ditching that product, I’m seeking recommendations on a specific product(s) that has proven to work. Frankly, I just need it to control the volume on the Sonos soundbar, regardless of the sound source.

I use my Apple TV remote, which talks to my Apple TV, which in turn communicates with my Sonos Arc via HDMI ARC and both controls the volume on my Arc, and turns on and off the TV set. But I could easily use the TV’s remote, and the volume commands would still be carried across HDMI ARC to the Sonos. 

Harmony announced in April of 2021 that they were no longer supporting their Harmony system, but to my knowledge, they’re not going away. Here is an article that points out that fact. 

Frankly, I still have two Harmony remotes in use, but I touch them fairly rarely, usually to reach my TV’s settings menu, or change HDMI inputs on the TV. Both are the puck based Harmony devices, and at least as of last week, have still been working, although I’ve not tried recently to ‘add’ a new device. Frankly, with the increased use of the CEC standard, there’s less and less purpose to this style of remote, at least in my life. 

If it’s just that, can’t you use your TV’s remote control? I’ve got a Sony TV remote, and a Harmony 650 programmed that way too, giving volume up or down from either device even when listening to streamed music or music library. 

If memory serves, the IR is only active when the TV input is active. But I’ve never adjusted my Sonos volume using my Harmony remotes when using the Sonos for music, I’ve only ever used a controller on either a Mac, an iPhone or iPad. In fact, I’ve never set up the Harmony to control the Sonos. So my input may not be particularly valid to the OP, who wants “to control the volume on the Sonos soundbar, regardless of the sound source.”

It used to be that Sonos made a remote, but they’ve retired those in favor of mobile devices, which everyone seems to have in their pocket. I suspect that at some point, those physical remotes ran out of onboard memory to reflect all of the changes that Sonos made as they evolved their open architecture. 

Sofabaton X1 will control one Sonos Soundbar no problem. I’ve been using it for several months now without issue, purchased from amazon.ca  You do need some remote program understanding as the support documentation lacks. It is nowhere near the Harmony Code Database, but most things are there. Besides, if you have all your original remotes and of course use your Harmony, you can teach this X1 any IR code. Note: you need to program the mute key with a long press for the “unmute” function.