I think people would be very surprised at some of the devices that would Jam a GPS.
I was once gifted a "Kogan Action Camera", basically the Kogan version of a GoPro. First time I used it in an Aircraft all seemed fine, I started up, when to start up the trusty 96C and couldn't get a signal... not unusual, sometimes it took a while to get a lock, didn't really require it anyway as it was a route I'd done 100 times before and was nice clear weather. Took off, still no GPS Signal, not a single satellite, really weird as it would normally be fine by now, something in my mind thought it could POSSIBLY be the Camera, I turned it off and not 5seconds later I had GPS Signal again!!
I was able to reliably repeat this, watching the signal meter, turn the camera on, 5 seconds or so later all signals dropped to 0, turn it off and signals returned. The Kogan Camera had absolutely no transmitting capability, neither Cellular, Bluetooth or otherwise and would block it even when placed 2m away outside the fuselage and mounted under the wing, had to get it at least 4m away to not effect the GPS.
I would love to see the tech the US Defence Force are presumably using to test this intereference, for this range it has to be pretty powerful! I suppose they've figured out GPS isn't the only mob in town now and just turning it off or degrading it won't have the effect it used to.