Did you try and change the SonosNet channel?

Change your Sonos system’s wireless channel | Sonos

The WiFi6 mesh points might accidentally be in better physical locations, avoiding some interference.

I changed from channel 1 to channels 6 & 11. It didn’t help SonosNet in my setup. I still had lots of dropouts.

“The WiFi6 mesh points might accidentally be in better physical locations, avoiding some interference.”

Possibly. But the bigger reason I think is that the WiFi6 mesh network is a lot more robust than SonosNet- it provides a strong wifi signal throughout my house. Makes sense to me because it’s much newer technology than the old SonosNet.

I’ll just say that if you’re having dropout problems grouping older and newer Sonos speakers, try a newer WiFi mesh system and eliminate SonosNet (the dedicated WiFi network only for your Sonos speakers). You can easily do this by powering down all your Sonos speakers, force-quitting the Sonos app on your phone and/or computer, disconnecting the Ethernet if you have it connected to a Sonos speaker (or if you’re using Sonos Boost), and powering everything back up. That forces all the speakers to connect directly to Wi-Fi. Works for me!

I used to be an advocate for SonosNet many moons ago, but these days I too now use my Home Sonos setup on a WiFi-6 mesh. Device discovery is a lot quicker, not least as I’ve steered a majority of my Sonos products onto the faster 5Ghz band, with the exception of a couple of older products that only support a 2.4Ghz connection, such as the Beam (gen1 & gen2). 

A further thing I have also done, is ensured the SNR level to the local WiFi AP’s from every Sonos device surpasses the 45dB (strong wireless connection), as seen in the Sonos mobile App. See this link for additional details:

https://support.sonos.com/en-us/article/understanding-the-network-details-section-in-the-sonos-app

Doing this and ensuring my WiFi channels are always optimal around my Home has meant the Sonos controller Apps open and discover my 20+ devices and services much (much) faster than the old S2 and/or S1 Apps.

Additionally, with my particular setup, which consists mainly of Play:1s, Alexa works significantly faster as a voice controller- it’s essentially instantaneous. The Sonos voice controller is so slow that I really can’t use it. 

And, controlling my Sonos system with the Sonos Controller for Mac is significantly faster than using the iPhone app. It’s almost instantaneous. The iPhone app is working well, but not as well as the Sonos controller for Mac, which makes sense given the differences in operating systems and app design.