After you apply this update, Microsoft Skype for Business Server 2015 will provide custom policies to the UCWA client (such as the Skype for Business for Mac or mobile client). The custom policies are configured through the New-CsClientPolicyEntry cmdlet. This enables UCWA clients to support custom policies like Skype for Business App for Windows.
How to get this update
To get this update, install the May 2019 cumulative update 6.0.9319.548 for Skype for Business Server 2015, Web Components Server.