Have you tried not using IVS and making sure the onvif trigger is working from the basic motion detection as a starting point?
I'm using this camera with SMD and it's working on the latest BI release as well as the integrated DeepStack.
When I first set that up I had to play with the camera...
I use a USG. My cameras are all on their own vlan / subnet so they can't see the rest of my network. I use firewall rules on the USG to drop connections from that vlan to everything else including the internet. Works fine.
With a Unifi USG you still need a managed switch to configure different...