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 RTSP somehow, but I don’t remember exactly how. I see some references to it in some quick searches though. Maybe start here (some blog) or here (Stackoverflow question)?

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.

Sorry about your cat. We typically have a Rover stop in to check on our cats when we’re gone for a bit; it’s nice to get them some human interaction and they always send pictures and give updates.

I personally have a camera setup inside that just streams to HomeAssistant so we can check on them ourselves when we’re out just for the weekend. I disconnect it when Rovers are stopping by though because I don’t want them to feel spied on. No need for anything fancy really, but if you really want NVR I just use Frigate (for other things, the cat camera really is just a stream). It’s free and open source and really easy to set up.

WireGuard is a very easy way to set up the access. My router has just the single WireGuard UDP port forwarded