UI Suppression modeFor some good background on UI Suppression mode as it applied to Lync 2013 - see here
Official documentation is here.
The Registry location for the UISuppressionMode flag for the latest client is HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Lync\UISuppressionMode - I found this using the still awesome sysinternals process monitor tool
Skype for Business 2016 client SDKIt seems that Microsoft has not updated the documentation for the client SDK for the latest release.
According to a few peoples experiences here and here the Lync 2013 SDK seems to work just fine.
Beware though as this could mean it will be depreciated in the future.
Firstly you will need to install the Lync 2013 SDK. Essentially you need to download the SDK here and extract it using 7-zip (or whatever). Then install the msi for your platform.
Lastly you need to add the missing registry keys that the Lync 2013 SDK looks for to determine the client state :