I published a blog post few months ago regarding changing the Calling Application Preference using PowerShell. I also published another post about the New Teams and SfB Admin Console.

Today, I noticed that when you I tried to change the setting as per my post, the previously allowed calling application preference TAGs were not supported anymore; see the error notification;

TeamsInteropPolicy no longer supports granting policy instances in which the value of CallingDefaultClient differs from the value of ChatDefaultClient. It also no longer supports granting
instances in which AllowEndUserClientOverride=true.
Only these three instances are supported:
DisallowOverrideCallingDefaultChatDefault
DisallowOverrideCallingTeamsChatTeams
DisallowOverrideCallingSfbChatSfb
In the near future, the other instances will be removed and users will be automatically assigned one of the supported instances. If you are sure you want to temporarily grant a
non-supported instance of TeamsInteropPolicy, you can override this warning with -Force.
+ CategoryInfo : NotSpecified: (:) [Grant-CsTeamsInteropPolicy], ArgumentException
+ FullyQualifiedErrorId : System.ArgumentException,Microsoft.Rtc.Management.Xds.GrantTeamsInteropPolicyCmdlet
+ PSComputerName : adminau1.online.lync.com 

The most apparent reason for that I believe it should be my tenant is being upgraded with latest Microsoft Teams & Skype for Business Admin Centre, which supposed to provide GUI based controls for the same functions.

as per the error description it still allowed me to make Teams as the default application for calling/chat by using the Tag:DisallowOverrideCallingTeamsChatTeams for the time being. But, the error further says this all policies will be removed soon, which means we will be opted with using the Admin Console instead.

Just a heads-up for folks out there in the middle of SfB to Teams transition.