Airport Express
I got an Apple Airport Express. Can I use the internet if I use the USB with SIM card reader?
Question marked as
No.. it must be plugged into a router or modem by ethernet.. or connected to another Airport router by wifi.
Apple do not support using USB 4G modems.
You could however use a suitable 4G modem or tether an iPhone with a Mac and connect the Airport to it by ethernet to share internet with your network. But it is for emergency setup .. not normal internet usage in your house.. if you need to use 4G etc service for internet the best method is to buy a suitable hotspot device from a service provider with cheap data plans.