I followed the steps in this article and my Sonos system is now fully functional on a T-Mobile 5G Home Internet Wi-Fi network. I am running 4 One’s, 2 Five’s, 1 Amp, 1 Move and 1 Playbar.
I believe the key was shutting all components off and then powering them up in RESET mode. This created a clean slate for connecting to the T-Mobile 5G Gateway.
I just completed this today (Dec 10 2023) and will report back on stability over the next couple weeks.