I searched this question. There seems to be known problems connecting router with iPhone:
USB tethering doesn’t work
Connection to a hotspot provided by phone lasts only few seconds before it’s dropped
As for USB tethering, the phone is not recognized in the web interface. The LEDs remain off. I connect the phone to usb 3 power plug. Otherwise I need to connect USB3 on router to power source and use a USB3 to USB3 adapter to connect USB3 in iPhone to USB2 in router?
I upgraded to the latest firmware in the router and reset network settings in iPhone. The issue remains.