I do not have a security gateway in use, but 2 US-24 switches and 3 APs. They are all connected with normal Cat 6/7 network cables. SFP is mainly needed when the speed of the normal ports is no longer sufficient.
The SFP's (the US-24-250W has 2 of them) are needed if you want to connect several switches.
There are a few details on the official site:
https://dl.ubnt.com/datasheets...