I saw this posted earlier while I was testing out a pair of replacement Pi3 boards I just received today. Always had great luck with the pi's but on my last order both of the pi3 boards were DOA while the pi4 worked just fine -- never heard of that happening before! Fortunately both of the replacement boards booted up without any problems so I guess it was just my bad luck.

Not exactly an easy project, but if you really want to go crazy you could look into rtlsdr, specifically in picking up the signal from weather satellites. One of my new boards is to replace the one from my own project that had to be re-used for something else in a pinch, so I'm working on getting that back online today. Otherwise setting up a PiHole is a popular project, or even using your pi with libreElec to watch downloaded video content on your TV.

If you have your pi being used for other things on your network, there are simple projects like MRTG which creates charts and a web page you can use to view network traffic but I'm not sure if that will tell you when your ISP connection goes down.