If you want to apply conditional validation on 'MAC Address' or 'Local MAC Address', then you need to add 'Device' input as 'Laptop'
{{macaddressinfoForm.controls?.device?.errors?.mac.message}}
If you want to apply conditional validation on 'Local MAC Address' then you need to add 'Device' input as 'Laptop'.
Conditional Expression with type 'string'
{{macaddressinfoForm.controls?.localMacAddress?.errors?.mac.message}}