If you're talking about the Network Scanner function in Recon, I suppose you don't need to supply the actual credentials it would use to SSH into the machine and enroll it. Just provide some bogus credentials and see if it locates the Macs on the network but it will fail if trying to enroll them. It's been so long since I've used the app or that feature honestly that I can't really tell you for sure how that would work. But I know it can't enroll with the Network Scanner feature unless it can make a successful remote login connection to the device.
You could also look at a tool call LanScan that you can find on the App Store. You'll need to buy a paid version of it to unlock the full features, but it will scan your network (or IP range) and determine the makes/brands of devices it finds. It lists the IP address, hostname if applicable and MAC address, as well as a few other items. It will find anything in the range you tell it to scan, so it will list out things like routers and switches, smart TVs and whatever else may be in the same IP range. It certainly won't enroll anything since it has no functionality to do that, so it might be a good option to look at. As I mentioned though, to get the full features you'll need to buy a license, but it's only $6.
