The Sonos app lag is specific to the phone model and Android version.  Permanently resolving this issue is hopeless.  The ultimate solution is to purchase a new phone.  The Sonos app conflicts with some versions of Android and some phone models.

I had this exact problem.  My symptoms matched those listed in this topic: slow app startup, frozen app, devices not showing, etc.  My Sonos app was unusable.  At times I got the app working just enough to activate my Sonos speakers.  Trying anything more was an exercise in frustration.

I waited for updates, tried app rollbacks, reinstalled the app, studied support posts, tinkered with my account, tinkered with my router, etc.  I found no permanent solution.  The Sonos app problems lasted nearly a year.  Eventually I happened to replace my smart phone.  The Sonos app now works fine on my new phone.  The Sonos app problems did not carry-over to my new phone.

My previous phone (with the Sonos problems) was a Motorola G Power 2020 running Android.  My new phone (without the Sonos problems) is a Google Pixel 8 running Android.  The Sonos app was unusable on my Moto-G Power 2020.  The Sonos app functions properly on my Pixel-8.  No other equipment or account settings were changed.

I’d be curious if folks with this problem have the same trouble with my own just-released Android app (see profile).