It would be great if some sort of alert could be generated/sent if the Ping Watchdog feature actually detected that an interface was down, mobile data can be expensive so being notified if/when the device lost ethernet communication and switched to Cellular would be really useful.
It would be helpful if you could specify which product you are talking about. Was this supposed to be followup to your existing RAK7258 thread?
I assumed that as a feature request, it would apply to all products but the range has a lot more than I thought. I’m specifically talking about the RAK 7258.
For the RAK7258, the overlay filesystem will let you make additions such as adding an /etc/init.d type service (either a simple shell script or specifically targeting OpenWRT procd) which checks network interfaces and then reports status via a mechanism you prefer. The “developer gateways” based on a pi rather than OpenWrt platform give you even more flexibility both in the OS which is basically debian, and that you’d typically be installing via a script that builds from source.
Standard gateway backhaul doesn’t really define a channel for this kind of information, so actually doing it would have to start with deciding how you want to notify yourself, eg, some RESTful API you want to hit routinely or in case of issue, an MQTT broker, or something else.
In essence, given that what you want is (perhaps surprisingly) not a feature of the relatively same across the industry functionality of gateways, the first step to implementing it is deciding how you want it to work. All of my gateways run custom daemons which interact with the unique proprietary infrastructure I find useful, but that’s not the same infrastructure you might use.