Switching between WAN and LTE?

I am working on a project that requires a remote connection.

I planned to use an OpenWrt router that has LTE capabilities and has a long-range WiFi Router hooked up to the WAN port. I wanted to ask if there is any possibility to configure it in any way to use the WiFi router (that could also just be set to bridge mode if that is better) if it has a signal and if that signal is interrupted, switch to LTE?

My initial testing had the result that LTE is a bit slower and I also worry about data caps, and in most cases the WiFi connection should work.

The LTE should only be a fallback in case the WiFi gets out of range.

I plan to use the GL.iNet Spitz (GL-X750) as my LTE router and the Ubiquiti rocket M5 as my WiFi Router/Bridge


Start by reading here:

What you need is named "failover" so that if main link is down it falls to a backup link.