Most substations are defended by a chain link fence with maybe some barbed wire at the top. There are plenty of tools that could disable them, both firearms and otherwise. I can't speak to how many you'd need to take out to collapse the national grid, but I can tell you that region wide problems can be caused with an attack on one or two. Our infrastructure is ridiculously vulnerable.
My Sibling in Christ, giving us less for our money and giving them more control over our lives is the intent of all of this. Time to seize the means of computation.
Personally I've never used PopOS so I can't speak to it.