Honestly I wouldn’t even go so far as home assistant. Do you have any IP cameras or just USB webcams? If you have IP cameras all you need is the VPN and then just access them as if you’re at home. If you only have USB webcams, you’re going to have to stream the content and I believe ffmpeg is actually capable of taking /dev/videoX and serving it over HTTP somehow, but I don’t remember exactly how. I see some references to it in some quick searches though.

Another thing to remember is that you’re going to be limited by your upload speed. If you’re not on fiber and in the US that’s likely going to be pretty bad, so set your resolution and the like accordingly.