Basically, your Symfonisk lamps are a mix of the lamp part which I believe connects to your IKEA gateway and works with HomeKit like any smart light. But the speaker part is of course a Sonos speaker, and Sonos doesn’t support HomeKit, only AirPlay 2.

That means you can see and control the light in the Home app, but the speaker won’t show up in HomeKit. You can still stream to the speakers with AirPlay 2, and control them in the Sonos app, it’s just that Sonos doesn’t support full HomeKit control.

https://support.sonos.com/en-gb/article/use-siri-to-control-sonos-speakers

It's not quite as you say. I have multiple Sonos speakers in my other home. Sonos speakers, but not the IKEA Symfonisk, and they are visible in Homekit. So why doesn't HK see the IKEA Symfonisk, but the Sonos speakers do?

Interesting. Try this:

• Open Control Center on your iPhone

• Tap the AirPlay icon while playing music

• Select your Symfonisk speaker

• Once you’ve streamed something to it, go back into the Home app, and check under the Room settings or AirPlay speakers list

It may well then show up there the same way as your other Sonos speakers, just not as a full HomeKit accessory, because as far as I know Apple doesn’t allow third-party speakers to behave like that in HomeKit (i.e. not a Sonos limitation, but an Apple one).

​@Rhonny , thx. I’ll try this but only next week. I'll let you know about the results.

You need to Add it to Apple Home App, as per the Sonos Support link above.

Note the second link, if you rename in Sonos App you have to also rename in Home App.

​@Pantagruel 

Maybe go for what ​@craigski has posted first. And failing that, look at mine…?

​@craigski

​@Rhonny 

THX guys. I will test your advice next week and let you know the results

Don’t get too excited, the ‘integration’ is limited, from the link:

 This article covers how to add AirPlay-compatible Sonos products to the Apple Home app, allowing you to use Siri on your iOS device to play and control Apple Music on Sonos. Note that this will not add Siri to a voice-enabled Sonos product or let you control them directly within the Apple Home app.

I want to set up an automation in HK that stops playback on my Symphonisk speakers when I leave the house. Is this possible?

I'd also like to be able to set up Symphonisk to play audio from my Apple TV 4K. Is this possible?

I personally just use voice commands to ‘stop' music whilst getting ready to go out. If you want to fully automate, maybe take a look at something like homey

Yes, via AirPlay.