Exporting a virtual machine (VM) as an OVF file from vSphere 8.x and importing it into vSphere 7.x fails with the following error message:
The VM being imported into the vSphere 8.x environment is configured with virtual machine hardware version 21, which is not compatible with vSphere 7.x environments.
KB article 312100 details the rirtual machine hardware version compatibility with vCenter Server versions:
After the VM has been exported as an OVF from the vSphere 8.x environment, use the steps detailed in KB article 393287 to edit the VM hardware version in the .ovf file, update the checksum of the .mf file, then import the OVF into the vSphere 7.x environment: