I have a project where the only internet available is through a cellular connection. They have a Rogers 'rocket hub' router which connects well to LTE and provides adequate bandwidth with unlimited usage. The router configuration is very limited, with most of the options greyed out. There is an option for bridge mode, but there is an error message which says please 'disable ppp' to change to bridge mode. There does not seem to be an option in the router to 'disable ppp'. I can disable wifi, but I am not able to disable DHCP server.

I have installed a decent size control4 system here, and planned to use an araknis 110 router with a pakedge 16 port unmanaged switch. I tried lots of different configurations with settings in the araknis router, such as assigning WAN address as a static LAN address from rocket hub router. I then setup the LAN on the araknis router to a different range ie, LAN address on rocket hub is 192.168.1.1 and LAN Address on Araknis is 192.168.2.1. I also added the Araknis WAN address to the DMZ in rocket hub.

Every configuration I tried resulted in no internet on the Araknis side of the network. I ended up just reseting everything, and by-passing the araknis router, and have rocket hub connected directly into the pakedge switch.
everything is currently operating fine including the wifi access points, and control4 system. but I would like the ability to reserve dhcp addresses, and forward ports, but do not have these options in rocket hub router.

The model of the rocket hub is ZTE MF28B

Has anyone worked out a solution to a similar issue ?

I've come across router->router combinations that will choke on 192.168.x.y->192.168.v.w configurations. Try setting your router to a 10.0.s.t subnet.