I'm not sure about self hosted specific. There is a device called WiiM. Works with most of the major streaming services. I believe they're also working on plexamp integration too.

The Google Casting protocol is proprietary (and indeed the outage was caused because the system that verifies a receiver's "legitimacy" broke down lol) so AFAIK there is no Open Source solution that can replicate the functionality. At least so far.

I always thought since the cast button on Spotify/tidal/etc. is a Google thing it would only ever work with the Chromecast protocol.

This is the closest thing I've heard of that does some sort of casting. AFAIK it doesn't replace chromecast. I've never actually used it.

My solution to this since my house is small is to use an amp that supports multiple speakers that all the devices connect to and then wire speakers through the house. I've thought about connecting the amp to a small computer and streaming the audio to my sheds using ROC. The neat thing about this solution is I can play my records and tapes too and listen to them seamlessly between rooms.

I've never had any luck finding anything open source / self hosted that actually works reliably. The best I came up with was an Nvidia Shield, which at least allows to you to run stuff like Kodi, Jellyfin, and Smart Tube Next (ad blocking YouTube client).

It’s iOS-specific, but if your family happen to have iOS devices https://github.com/mikebrady/shairport-sync works amazingly with Rpi ZeroWs. But I’d spring for the 2W version for some breathing room, if you could. All the iOS apps I’ve used are able to play to an airplay2 group in sync, but I don’t have either of the apps you called out specifically.

I'm in the same boat. I'd say that my current setup is still not back to 'normal' since the issue with the certificates on the second gen devices.

I was able to cast to a CCA yesterday for a few hours after rebooting it again.

I have, over the years gone all in with the CCAs which is great when it works but sucks being tied to google. I have 11 active running CCAs connected to two separate 12 channel amps that have wired speakers throughout my house.

I use Google Mini's in those locations with their default speaker set to the CCA feeding that room's speakers. I also have groups "Basement" "Upstairs" "outside" etc that allow me to group them into larger zones. This is all very awesome when it works, but like we found out last week falls apart when there's a problem on that house of cards.

We can via apps directly manually 'cast' from YTM or Spotify or whatever (podcast app) or just ask the mini in the room to play music or play music on 'group speaker name'.

I got here from 'Casatunes' which when I was using it, was a PCIE card you installed in a windows machine and then installed their software (that ran on IIS) and it created a web service where the PCIE card (a soundblaster) had 6 3.5mm jacks (6 zones) as output, and then the software allowed you to assign 4 different inputs. Biggest issue I had with it, is as I moved from Sirius XM to streaming the service I opted to go with wasn't supported. Eventually I migrated to the CCA approach.

I'd love a way to setup 11 Pi's (although not at today's prices) with some open source protocol that replaced googles casting. The problem then would be getting some local speaker (google mini) to interact with it, or even your phone (spotify/ytm to 'cast' to that open protocol). Whatever the long term solution it would need to be easy to use or nobody but me will use it.

You can get standalone Bluetooth devices that just output audio.