@Denzerini

That‘s not some kind of magic as the Sonos connect or port does have a regular line out. There you can connect a bt transmitter same way as any other device with a line in. 
Bt transmitter to bt headphones also is a regular thing. 
But why doing that? There are quite more easy to do solutions like using your headphones directly with the smartphone. 
But yes… if you like, you can do so. 

I use Sony headphone linked to a 1Mii B03 Pro Bluetooth long-range transmitter that’s cabled to the Sonos Port. The Sony headphones have dual BT connections, so they can be switched to a mobile device (iPhone/iPad) too using the Sony Headphones App. I mostly use Alexa voice assistant to playback and control the music through the headphones.

The BT long-range transmitter can reach all the rooms and front/rear garden areas of our Home too, so it’s a nice thing to have and not disturb neighbours at night, or other family members watching TV etc.

@Ken_Griffiths 

Yes, of course a very individual decision of need. For you and those who like to use their headphones with Sonos there’s the way to it. And better to have some more options than less.

Great to know that this setup will work just fine. Frustrating that two different calls to Sonos resulted in both insisting that BT headphones are not compatible with their products, so will not work (even after I explained how it should work -- maybe they’re trying to stall customers knowing that they will soon be releasing their own BT headphones soon!).  I appreciate the suggestions to make this happen and also for the BT long-range transmitter recommendation.

I probably should have mentioned the Sonos equipment that I currently have:  Arc;  Four Sonos-1’s, and a Sub.  No Ports, Amps, etc. so looks like I’ll need to purchase a Port box.  I’m looking to add high-end BT headphones so Focal or B&W, likely.

@Denzerini 

I think you should go with the Sonos Port as the device of the actual line up. The older S2 Sonos connect (2015 or newer) also would do the job, but it got to it’s limits because of old hardware. 
 

@Denzerini 

PS: 

The reason for your answer from Sonos support is, that they don’t recommend or support unofficial setups using 3rd party devices in between a chain of supported devices. That’s why for example hdmi switches / an audioextractor or even BT transmitter just work fine but aren’t supported officially. 
Sonos can’t guarantee that all of these different devices will work with their products. 

I understand and that makes sense. However, it sure would be nice if Sonos support provided a response in the same manner you did, instead of just insisting that BT headphones won’t work, period. Their response is misleading by presenting a dead-end to the customer, instead of a cautious warning that doesn’t squelch hope.

Thanks again.

Remember any analogue connection to Sonos ads a 75ms delay. On music Sono corrects this, for TV viewing/listening it does not.

Another good BT transmitter is the Fiio BTA30 Pro - it’s a little more expensive, but has a Coax connection for Digital S/PDIF output from the Sonos Port, but do note @106rallye’s comment about the lip-sync issue with TV Audio, which is correct. I am able get around that issue in my own use-case, as my LG C9 TV has its own BT transmitter that outputs direct to the Sony headphones, albeit there’s a minor inconvenience of having to disable the CEC protocol (Simplink) in the TV Settings, but I can happily live with doing that.

That’s not really what’s going on.  TV inputs (digital) are played in the connected room almost immediately, while other grouped rooms are delayed.  Other inputs, whether they be analog or bluetooth are delayed everywhere.    What OP is wanting is output from Sonos though, which isn’t delayed at all (in relation to other Sonos rooms).  If you do see a delay in output, it’s due to the 3rd party devices used, not Sonos.

Wow, this is a critical point since I also wanted the BT headphones for my LG OLED. Thank you for this alert. Sonos new headphones (assuming they’ll be Bluetooth) will probably correct this delay for TV listening. So I guess I’ll have to wait for their release, rather than risking 3rd party incompatibility.

This is getting a little over my non-technical head. Are you saying that 3rd party BT headphones can work seamlessly enough with my TV? If so, what required feature should be looked for in order to achieve a successful operation?

Why don’t you bypass Sonos and connect your headphones direct to your LG OLED TV, using the TV’s Bluetooth connection, that’s what most people would do and then simply connect to a BT TX linked to a Sonos ‘Port’ output for playback of all your Sonos Music? Most headphones these days cater for two connections and that would make switching between the two, a doddle.

That configuration does seem to be the best solution for third-party BT headphones. Since the Sonos headphones are rumored to be officially announced within the next couple of months, I’ll just sit tight for now and see what their product looks like, and how it initially reviews.

This board has been extremely helpful so thank you all for sharing your relevant experience here.

Just as a comment, that rumour about headphones has been floating around for at least a couple of years, potentially longer. 

…and perhaps there’s no reason to not have another set of headphones anyway. One to wash (charge) and one to go.