I have noticed an odd behaviour in the last few months that I put down to the New Meeting Experience (NME) disappearing issue, that has been discussed. Most if not all users in my tenant have the NME, I had it but now I don't. That was until last night when I connected to an older machine I hadn't used in a while and I discovered that the NME was still functioning on that device. Same account but not on our AD. On finding that, I connected to one of my test VMs that has never had Teams installed, install Teams and the NME is present. Again same account this time in our AD.
I notice that neither has the Teams Machine Wide Installer, so on the non-functioning machine, I removed Teams entirely, the Teams Machine Wide Install, MS Teams, cleared all the Teams folders from %appdata%\Local, LocalLow and Roaming. Restarted the device, ensured I was signed out of all Teams clients across all devices. Left it overnight and then reinstalled Teams this morning (using the same installer as the VM) Still no NME on the device, but the VM still has it.
There are differences between my main device and the VM, differing Office versions main device is on O365 Click-to-Run installer Semi-Annual Channel, the VM is on an Office 2016 MSI Installer version. But other than that built from the same deployment image.
To me this is shows that this is not the same "disappearing" issue where the feature has been pulled from some users within the tenant. But that there is a setting, reg key, GPO or something that is preventing the NME on some clients, but not others. I've even tried copying the desktop-config, settings and storage json files from the working one but still no luck.