ESXi 8.0x
This issue occurs if a snapshot was taken on a virtual machine when the vSphere standard port group existed, but has since been deleted.
This could also occur, if VM template(s) still exist, that were created when the VM(s) were on the original standard port group which have since been deleted, or no longer associated with the VM(s).
If snapshots are removed from the VM, and still, original standard port groups are still displaying, check for VM templates, and remove them.
To remove VM template(s):
1. Right click the template and select 'Delete from Disk' or 'Remove from Inventory'.
Please find details related to deleting snapshots from the link here : https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/8-0/delete-a-snapshot.html
Please check this guide on removing or deleting VM templates: https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/7-0/vsphere-virtual-machine-administration-guide-7-0/managing-virtual-machinesvm-admin/adding-and-removing-virtual-machinesvm-admin/remove-virtual-machines-from-vcenter-servervm-admin.html