Redundant backup

[Reith]

I would like to know what is the best Mobile router to use.  So it can automaticall kick in when my cable internet goes down.   I currently have a Netgear Orbi RBR50 wireless mesh system

[CrimpOn]

That's sort of a complicated question and depends a lot on how tied you are to the Orbi 'router' functions and to the existing RBK50 investment.

The other key consideration is which LTE data service is available in your area.

There are numerous WiFi routers which include an LTE modem and also a conventional ISP connection, such as the RBL20 (see page 21 in the user manual) https://www.downloads.netgear.com/files/GDC/LBR20/Orbi_LBR20_UM_EN.pdf  and page 24 in the NBK752 manual (https://www.downloads.netgear.com/files/GDC/NBK752/NBK752_UM_EN.pdf )

These are we used to call a "Fork Lift Upgrade". i.e. they take the place of the existing RBR50 router.

Alas, the regular Orbi itself has no concept of multiple ISP feeds and 'failover'.  In order to maintain the current investment, one solution is to front the Orbi with something like a Ubiquiti EdgeRouter which supports multiple ISP connections and add a regular LTE modem.

Geez. I'm not even sure who would be a good person to ask.  You might start by browsing the Netgear community forum for LTE modems.  Maybe someone has posted on their about their solution to this issue.

https://community.netgear.com/t5/Orbi-4G-LTE-5G/bd-p/en-home-orbi-lte 

https://community.netgear.com/t5/Mobile-Routers-Hotspots-Modems/bd-p/aircard