It's really difficult to find solid guidance on how secure that is. E.g. tag the port on the switch, run a cable to the device so that it doesn't know there's

It's really difficult to find solid guidance on how secure that is. E.g. tag the port on the switch, run a cable to the device so that it doesn't know there's a vlan involved, block routing between vlans. As far as I can tell that's probably good but might not be.