WARNING : No target specified, deploying to emulator
I had another developer tool opened (Chrome Inspect) and it "ate" the connection. In my case, just closing the Chrome Inspect panel and running ionic run android
worked.
I solved the problem.
Here is what I did:
I typed into the command line: adb devices
(located in the "platform-tools" folder in the Android SDK) which returned me an empty list.
So I installed my phone's drivers, which I downloaded from the vendors homepage.
Now the list contains my device and the app is started on my mobile phone.
I had a different problem, with a very simple solution.
When plugging in your Android device for the first time, it'll ask you to trust the computer's certificate. That popup screen disappeared on me, as I was just getting a call.
Simply unplugging/replugging your phone and accepting your computer's certificate should do the trick!
Once you've enabled your device for debugging, make sure to turn on usb tethering on the device;
Settings > Tethering & Networks > USB tethering
This fixed the problem for me.