I would like to know if there is any documentation from Microsoft stating that SharePoint 2016 is compatible with Windows Active Directory functional domain/forest level 2012R2
Hello i found these documentations about SharePoint versions and AD and yes, AD on server 2012R2 is supported. There is only minimum version for AD and it is 2003 SP2.
- SharePoint 2016 Installation Guide - direct link for AD here
- There are confirmation for SP2010 and AD2016
- SharePoint 2013 had a minimum of "Active Directory 2003 SP2", which of course makes no sense, but that said consider Domain Controllers at a minimum of Server 2003 R2 with a forest/domain functional level of 2003 native.
- In this manual - Complete On-premise SharePoint 2016 Setup Guide, step 2: Instal AD 2012R2
I hope these posts are enough for You.
Hope it helps!