The particular problem with organized resistance movements is the ever present monitoring of everything everywhere. This is where AI has a one up on us meat bags. When everything you do is logged and correlated the leaders of the resistance may find it hard to hide.
Simply put Ukraine is but a slight taste of the future horrors of war. Once you start mass producing things like smart mines (think something like a drone with a camera and a bomb) and just tell it to 'kill humans' your EM noise doesn't even matter, it's a stand alone unit. Things like this will just sit around a few day and catch you moving and then blow up on you.
It is harder that just blowing stuff up, but when one side is using killer robots and other advanced electronics tech it doesn't seem like much effort in comparison. We already see criminal elements making guns and drugs and narco submarines, a fast explosive and magnets doesn't seem beyond reach to me.
the fact that EMP blasts are not used in Ukraine, by both sides, to defend against drones also shows its not such a good idea
Maybe smaller scale DIY EMPs wouldn't be as effective as I think, they would have to be pretty close to their target to do real damage to non-radio devices, however I think collateral damage is the biggest reason we don't see them.
Drones are weak and fragile enough already that it just easier to shoot or blow them up rather than try to lob a grenade sized EMP up near them, a regular grenade explosive would be similarly or more effective without the extra complexity. But something like a mobile turret platform or multiple smaller ground bots I can see it being the best option.
It's a supreme delusion that it can't. Military tech isn't in the 19th century anymore.