Dear @MarcoCiani,

I was looking to a way to force a specific device to always associate to a specific AP on my network.

I don't think this is an option today (and honestly I don't know if it's interesting for many others :) )

I'm afraid that there is no such option on the Omada devices.

Edit: 

If you want to force the specific device to always connect to the same EAP, you may create a unique SSID for it.

And if the specific device supports, you can also try to hide the SSID after the device has been connected with the unique SSID.