I'm sure that won't work, as your /8 subnet is not under your /20 host network - ie the docker subnet is larger than the host subnet. A valid subnet would be /24 which would give you 172.31.80.1 - 172.31.80.254 usable addresses.
I am new to packaging Office. I have used the OCT and use KMS client key option.
The KMS server has been setup. Is there a need to point the KMS clients to the host name, or does this happen automatically?
I see the property AUTO_ACTIVATE, but from what I read this does not work with OCT and instead use the OCT "Add installations and Run Programs" using the command C:WindowsSystem32cscript.exe "C:Program Files (x86)Microsoft OfficeOffice16OSPP.VBS" /ACT