Hi Noprasetya,
According to my know, you are not able to activate Windows 10 2016 LTSB or Windows Server 2016 via Windows server 2008 R2. You will need to build a Windows Server 2012 R2 host to install the KMS key for Windows 10 2016 LTSB.
For more information, please ask help from Windows Server forum, they might have more resource to help you.
Bests,
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