Have you found out anything more regarding this? I'm in the same boat here.
The only option I currently see is MKR WAN -> Gateway -> A2A -> Arduino IoT -> implement web hook.
I find the support / documentation around the Gateway shocking so far, especially considering the price tag:
Only one container (pktfwd) supplied, seemingly locked, unconfigurable and sole purpose to forward messages from the gateway via A2A's network to the Arduino IoT cloud.
Missing background info on how containers are used in the setup.
Missing background info on what the listed packages are (I only get errors trying to install/update them).
Missing background info on how / when /where to access repositories.
There's the ability to upload sketches to the Gateway's RPi, but beyond printing something to the serial monitor in IDE, I don't really know what to do with it (no libraries, examples, handles to catch WAN messages and process).
Frustratingly ill-supported for a learning platform.