Working from home makes the reliability of your internet very important. And to keep my ISP accountable for downtime, I wanted to set up an uptime monitoring app.
But this problem was solved when I Installed a Pi-hole on my network. When your internet connection goes down, all your devices go into "panic mode" and ping the internet to see if the connection is up. And the result of that panic pinging is very visible on the Pi-Hole dashboard.
So, it appears that Pi-Hole is also suitable for minimal internet uptime monitoring.