I might violate your top “ideal solution” checkmark, but I have a raspberry pi running Motion Project (https://motion-project.github.io) on site and it makes an easily viewable webpage-stream. My Rpi4 can handle 2-3 video streams, with motion detect-video-save, periodic snapshot, etc. etc.
Not for the feint of heart, but it is the way I solved a very similar problem. I’m using random mixed brand of IP Cams, whatever was cheap at the time.
Thanks Bot!! that was awesome.