I am the same, used Little Snitch for a few years back in the late 2000s, I think like 2010 until a few years back when I moved fulltime to Linux. Back then, my parents had an iMac and I was the designated "IT" person to keep it running efficiently. My siblings had a bad habit of installing games and hack software on it for their games. I ended up purchasing a license and after the first few hours/days of configuring allow/block lists, it worked pretty well. It earned the label of "Little B*ch" from them since it would stop their gaming hacking apps from connecting and wrecking havoc. Eventually I learned to keep them on a standard user account and separate admin for installing software.

Long story you didn't ask for. Like I said, I haven't used Little Snitch in a while. I'll give this a whirl this weekend. What I have done over the past few years is run AdGuard Home on a min home server. This has helped keep ads undercontrol in our hoursehold and I have an easy "turn off adguard for 10 mins" in homeassistant for the wife so she can do some shopping online since it can occasionally break some sites, but overall they tolerate adguard and think it's a good middle ground. I have a few block lists, nothing too crazy or strict to avoid breaking most sites. On the desktops/laptops, they all run FireFox w uBlock origin.

How deep it was in the OS was exactly what I liked about it. I only wished it were open source so I know what exactly is happening with that level of access.

I’ve also wanted something like this. The challenge is with an external appliance you lose awareness of which process is initiating the request.

This is solvable to some degree but requires varying degrees of new complexity depending how smooth of a user experience you’re aiming for.