Sonos is NOT a proprietary ecosystem!

I think you are mislead by the term proprietary here. These articles probably refer to the use of closed-source software rather than lack of hardware inputs/outputs in order to connect to third party audio equipment.

I'm not sure I agree with that definition. Can you name any multi-room system that is actually open source?

Well, there are those die-hards who still use Squeezebox, though there is no widespread hardware availablity.

Note to Squeezebox fans: No need to jump on my answer, it was far more kind than reality dictates.

I don't think any of us can be sure what the articles meant by 'proprietary', without any context. I think we can all agree that Sonos can be used with some non-Sonos equipment.

I have seen the word 'proprietary' used about Sonos to refer to the fact that it used a proprietary wireless networking technology - SonosNet. At that time it was not possible to use Sonos other than by using SonosNet. That MAY be the use of the word 'proprietary' in the articles to which the OP refers.

God forbid that Sonos should protect their hard earned intellectual property!

This whole thread is a bit pointless really. The OP has mounted a defence against an accusation that nobody is actually making, or regards as an accusation.

Well, there are those die-hards who still use Squeezebox, though there is no widespread hardware availablity.

Note to Squeezebox fans: No need to jump on my answer, it was far more kind than reality dictates.
Isn't that (sadly) the truth! There are a few high end pieces of kit that are still using LMS and coming out periodically, and the LMS itself is still under some development, but it's a slim menu of choices. 😉 Sad, because it's just so flexible and powerful if you were willing to do the setup.

I think they mean closed by there only being one hardware vendor, without a published interface to control it, and without full customization via said interface. It's not necessarily bad, it's just a limitation of the system, and there are tons of positives to Sonos as well. HEOS is just as closed, with less compatibility as its ecosystem is newer - and don't tell me that Marantz counts as a second vendor, as both Denon and Marantz are the same company (D&M Holdings). DTS Play-Fi and UPnP are the only protocols I can think of off of the top of my head where there's a variety of manufacturers, and I'd consider those to be, "Open," from the consumer's standpoint.

This whole thread is a bit pointless really. The OP has mounted a defence against an accusation that nobody is actually making, or regards as an accusation.

Do a google search for "sonos proprietary" and you will see numerous accusations. Many are not in the context of software vs hardware, and are misleading, in my opinion.

Well, there are those die-hards who still use Squeezebox, though there is no widespread hardware availablity.

Note to Squeezebox fans: No need to jump on my answer, it was far more kind than reality dictates.
Isn't that (sadly) the truth! There are a few high end pieces of kit that are still using LMS and coming out periodically, and the LMS itself is still under some development, but it's a slim menu of choices. 😉 Sad, because it's just so flexible and powerful if you were willing to do the setup.
.

Not quite accurate! You can run LMS & player on a 35 dollar raspberry pi. Add in the upnp bridge plugin and you can use a wide range of wireless speakers (including Sonos) as squeezebox players. You can control using a web gui, IR remotes, Android & iOS apps (and alexa voice). Slim menu of choices? Not really - iplayer, Spotify, Tunein, etc.

Another plus is active and friendly support via the LMS community forum, free from the acrimonious spats which break out on the Sonos forum!

Well, there are those die-hards who still use Squeezebox, though there is no widespread hardware availablity.

Note to Squeezebox fans: No need to jump on my answer, it was far more kind than reality dictates.
Isn't that (sadly) the truth! There are a few high end pieces of kit that are still using LMS and coming out periodically, and the LMS itself is still under some development, but it's a slim menu of choices. 😉 Sad, because it's just so flexible and powerful if you were willing to do the setup.
.

Not quite accurate! You can run LMS & player on a 35 dollar raspberry pi. Add in the upnp bridge plugin and you can use a wide range of wireless speakers (including Sonos) as squeezebox players. You can control using a web gui, IR remotes, Android & iOS apps (and alexa voice). Slim menu of choices? Not really - iplayer, Spotify, Tunein, etc.

Another plus is active and friendly support via the LMS community forum, free from the acrimonious spats which break out on the Sonos forum!

Is that like opening an app and tapping the screen?