As per the vSphere 6.5 documentation cannot export OVA templates. OVF templates is the only option.

This happened due to the removal of the Client Integration Plugin (CIP) which included a copy of OVFTool which ran locally on your desktop and was used to perform the export. In 6.5, CIP was removed and rather than relying on a client side tool to perform the export, this was now done natively within vCenter Server using the Content Library service which runs server side. The issue with supporting OVA as I understand it was that it would require additional space on vCenter Server to actually store the contents where as today, it is directly streamed to the customer for download. For small VMs, this may not be a problem but there are many customers who have extremely large VMs (several hundred GBs) and this could have a huge impact on VC.

If want OVA,then you use OVFTool and you’ll get the same behavior as 6.5 (which had the export run locally) as mentioned in the vCenter 6.5 release notes:

Workaround: Export the virtual machine as an OVF template, and then create an OVA template from the OVF template files. The following procedure describes this process using the Linux an Mac commands. Windows systems require installation of a TAR capable utility.

  1. Use the vSphere Web Client to export the VM or vApp as OVF template to the local machine.
  2. Locate the downloaded OVF template files, and move them into an empty new folder.
  3. Perform one of the following tasks to create an OVA template from an OVF template. — Go to the new folder and create an OVA template using the tar command to combine the files:

cd folder
tar cvf ova-template-name.ova ovf-template-name.ovf
tar uvf ova-template-name.ova
tar uvf ova-template-name.ova ovf-template-name-1.vmdk
tar uvf ova-template-name.ova ovf-template-name-n.vmdk

n refers to the number of disks the VM contains. ova-template-name.ova is the final OVA template. Run the commands in the exact order so the OVA is correctly built.

Note: The tar command must use the TAR format and comply with the USTAR (Uniform Standard Tape Archive) format as defined by the POSIX IEEE 1003.1 standards group.

— If the OVF tool is installed on your system, run the following command:

cd downloaded-ovf-template-folder
path-to-ovf-tool\ovftool.exe ovf-template-name.ovf ova-template-name.ova

Search for “vSphere Web Client does not support exporting virtual machines or vApps as OVA templates” under release notes