Just wanted to point out that these kind of "verify cables" questions would be on-topic at https://electrical.codidact.com/ as well, you might get a more advanced answer there. At the EE site you will also be assumed to have access to common tools like a multi-meter and a solder iron.

I was wondering about that! I'm a bit confused because unlike the Stack version, it's about electrical engineering questions, not electronics. Previously I think I saw people asking whether questions about electronics would belong there, and it appeared that the consensus was "no".

I also don't know that much about the exact nature of the signal carried on coax cables. I assume it's a low voltage digital signal... But I don't really know.

I did see online some people apparently use oscilloscopes for it, although I didn't get what exactly they were doing (I know how to use an oscilloscope and can get one). And yes, I have a multi meter and solder, I think it's fair to invoke them even here, they sell pretty good ones for $15 now :)

Oscilloscopes are for viewing/trouble-shooting the signals passing through the cable. They can't be used to verify the quality of the cable itself.