You could try Roon.  But it requires running a Roon server on another PC (i3 level - new cost around $300) on your home network, and there's a $15 monthly subscription charge. There isn't a plug and play solution.

I would give Sonos another month to sort things out before taking any drastic action.  Sonos quotes mid-June to restore local file library support.   Not ideal, but like it or not, without some tech. investment, either in new hardware or configuring, there aren't many workarounds. 

I think the facts are:

• Sonos is still the best option if multi room matters to you
• The app will get fixed but expect it to be later than Sonos are saying
• The competition will be more focused on improving the support to win disgruntled Sonos customers

So my plan is:

• Wait for Sonos to fix the app
• Don’t give Sonos anymore money (if I need something I’ll look on eBay)
• Wait for the competition to improve
• Eventually replace Sonos (assuming that in 5-10 years a viable alternative exists for me)

I agree Sonos will eventually fix things. But I’ll no longer buy Sonos speakers, and in time move away to a different solution for my music needs. I no longer trust this company to have my best interest in mind. They managed that in a matter of weeks with their lies and condescending communications. 

In 5-10 years it'll be be streamed music videos played on a holographic video player (& clunky old speakers will be for grandads).

Tidal is already half way there with music videos accessible via the Tidal native app. 

  The same fate will befall headphones clamped across your head like huge earmuffs (sorry Sonos & your $500 Ace wonders). 

Already the sound quality of unobtrusive earpods and ear clips is advancing by leaps and bounds

Yes, but in actual fact there are few if any alternatives which even match the Sonos ecosystem.  The current app is a mess but that can be sorted. 

The closest equivalent to Sonos is Bluesound but it fails in 2 main areas - fewer streaming services (no podcasts, no audiobooks, for example) and crucially for Internet radio it only has TuneIn (which can't deliver BBC, NRK, and other national services) and which is currently plagued by irritating & excruciating pre-roll advertising.  Sonos has a mix of radio based services, in comparison.

What users should expend their ire & energy on, rather than threats to dump, sell, sue & excommunicate Sonos, would be to point out which features are broken and require fixes.  

Yes, but in actual fact there are few if any alternatives which even match the Sonos ecosystem.  The current app is a mess but that can be sorted. 

It doesn't need to match Sonos ecosystem. It just needs to support the things I need. 

And it's not a matter that the app is a mess, and will be fixed. I'm sure it will be. It's a matter of trust. And that's gone. At least for me it is.

What users should expend their ire & energy on, rather than threats to dump, sell, sue & excommunicate Sonos, would be to point out which features are broken and require fixes. 

At no point did I threaten to do any of those things. You're reading thing that aren't there.

I'll continue to use the system for as long as I choose to. I'll just no longer (ever?) buy additional Sonos speakers. And in time move to whatever other solution is out there.

Sonos knows exactly what is wrong with the app, and don't need my input. The fact is they chose to force this mess on me anyway, and lied about it. Leaving me with a half functioning system.

I can no longer trust this company.