Bezsel, simple and easy, constantly having new features added.

I’d put a flap on the outside, just like some siding or something…

Tailscale and the other tools people mention is an option.

Another one that’s a bit more costly unless you already have it is UniFi gear can do site-to-site VPN which can make it pretty easy as well. Other router gear has it as well, UniFi just makes it easier. This would put each others networks next to each other and you could access them as if they’re in the same home.

And then of course just wireguard direct connection.

There’s a lot of options, matters only how DIY you want to make it.

Unless you have fiber at the house with the server, you’ll probably run into issues with streaming these ways without transcoding, even with transcoding gear… cable upload speeds and reliability can be middling.