This will guide you through the setup of the EdgeRouter X to be used as a switch. This currently is employed due to issues created by using a cheap switch with multiple UniFi APs.
Connect
Plug in using PoE injection or 12V 0.5Amp Power adapter
Connect computer to ETH0
Setup computer with 192.168.1.XXX address
Connect to EdgeRouter at 192.168.1.1
Probably need to accept any exceptions / agree to connect
Login with “ubnt” “ubnt”
Initial Setup
Run Wizards
Choose Switch
Select DHCP
Create new admin user (or keep existing users if changing from router to switch and not factory reset)