Blocking the .NET Framework 4.7 is quite easy via the following registry change:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\WU]
Microsoft just published the following article to remind everybody that .NET Framework 4.7 is still not supported on MS Skype for Business. They also provide steps to uninstall .NET Framework 4.7 if already installed.