I am using HAOS in a dedicated BeeLink PC. I purchased a couple of IP cameras that advertised ONVIF and RSTP and can be mounted outdoors. I connected them to my POE hub and they powered up, received IP addresses, and I was able to view them and configure them in Chreme browser.
The documentation is sparse and did not say how to access the RSTP stream. In the web browser it is all javascript so you can’t see the urls by hovering over links. But I used ODM and got a url I can use in VLC.
rtsp://10.0.0.34:554/stream1?username=username&password=password is the format.
Stream0 and stream1 are available, and I set stream1 up with low resolution and frame rate.
But when I try that in Generic Camera, it spins and never shows the video stream.
I did not configure a still image url, I don’t think it is required.
I feel like I am really close to success but it is still eluding me.
I was able to resolve the problem after resetting the camera to factory defaults, then configuring again for my purposes. Right now both cameras provide live streams and they only trigger events when the internal logic detects a car or a human in areas I have defined. Cars and people on the county road are ignored. When an event is triggered my office light changes. The camera also uploads snapshots to my HAOS ftp server. I have more work to do figuring out what to do with the snapshots.

