By default, the unit hostname is stellarmate.local
From StellarMate App, go to My Mates then select your unit. The hostname is the unit name. However, on some operating systems, you need to append .local and remove any underscores from the name. For example, suppose your unit name is stellarmate_f0220c
The hostname then becomes stellarmatef0220c.local
Another way to find the hostname is to open the Web Manager from the StellarMate App and you will see the unit hostname in the browser address bar.