Check type of traffic used by host and only allow to pass through main Wan connection

I have 2 wan connections, main, and LTE.  LTE is only backup, and don't want to unnecessarily use it.  I have IPTV subscription, and don't want it to use the LTE when main connection goes down.  I know the IP address of the TV box. 

Can anyone tell me find the application it uses?  Or is that how I begin to do this?

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[edited by: emmosophos at 6:19 PM (GMT -7) on 25 Oct 2021]