I have a few ASUSTOR NASes at my house, and I don't like installing a custom application just to identify the NAS so I can visit it's web UI the first time.
But behind the scenes, it's likely just scanning your network and matching any MAC addresses in Asustek's range. Which is easy to do without a third party app.
In my case, I can just run the following
nmap command in the terminal and it spits out a list of all ASUS/ASUSTOR devices on my network: