You may witness a vSwitch that is "Not Connected" within vCenter's Inventory and not associated to any specific VM:
Also known as a 'ghost' vSwitch.
vSphere version=7.0.3, build=24026615
This is due to Veeam related snapshots pre-existing configuration, that haven't rotated or been consolidated/deleted.
You may not be able to consolidate/delete any of the related Veeam snapshots as they're a component of their replication schedule. The schedule should clean itself up automatically and may not require any manual intervention. However, if the issue persists, you may need to delete the snapshot to remove this 'ghost' vSwitch.