Microsoft Lync 2013 / Skype for Business 2015: August 2019

Microsoft released Lync 2013 / Skype for Business 2015, v15.0.5163.1000
See description in KB4475564 and download from here x86 or x64

Microsoft Skype for Business Server 2019: December 2019

Microsoft released Skype for Business Server 2019, v7.0.2046.151
See description in KB4470124 and download from here

Microsoft Skype for Business for iOS

Microsoft has released Microsoft Skype for Business for iOS, v6.26.1.0001
Download from here

Updates for Lync Server 2013: September 2019

Microsoft released Lync Server 2013, v5.0.8308.1101

See description in KB2809243 and download from here

Microsoft Skype for Business Server 2019: September 2019

Microsoft released Skype for Business Server 2019, v7.0.2046.143
See description in KB4470124 and download from here

Microsoft Skype for Business for iOS

Microsoft has released Microsoft Skype for Business for iOS, v6.26.0.0001
Download from here

Microsoft Skype for Business Server 2015: August 2019

Microsoft released Skype for Business Server 2015, v6.0.9319.562
See description in KB3061064 and download from here