Need advice on a Wi-Fi Router that supports dual 3G/4G modems or an alternative?

Question

network hardware

Good time of the day.
The need to install a Wi-Fi router with two 3G / 4G modems indoors. so that in case of interruptions with one, it automatically switches to another.
The room is far from the city and there is no way to connect to the Internet in another way. Of the healthily working operators, these are Beeline and Megafon.
Since operators limit the amount of traffic on tariffs and, at least for moments that are inexplicable to me, sometimes one falls out then the other, so there was a need for a router that would automate this process. Searching the Internet for such routers, I did not find (maybe I was looking badly).
I ask for help, can anyone come across a similar device or problem?
PS: So far, only one thought comes to my mind. Take, say, a simple router with 3G support, put OpenWRT on it and a small Chinese splitter for 3 USB ports. And even then try with switching between two modems.
Thanks in advance.

Answer 1

Any router with 2 usb ports and OpenWRT support, for example WL-500gP V2, set up Multiwan on it and configure, auto start of the 2nd connection in case of a fall of the 1st.

Answer 2

Zyxel Keenetic with firmware v2 supports multiple Internet connections and allows you to switch between them if one of the connections drops.
Microtik routers also support this