Two strong locks and removing all quick releases is going to be your best option. I have a balloon tire ebike and due to the thicker frame and tires it's not often possible to lock it up well with just a single lock.
What I do on the rare occasion I need to lock it up outside is use my Abus bordo 6500 (very nice folding lock), Kryptonite U-Lock, and also a kryptonite cable with loops on each end. Both locks are somewhat portable and can mount to the bike. Ideally i'll have one lock going through the frame to pole,
one going through the rear tire to pole, and then run the long cable through the seat and both tires, locking the loops into the u-lock or folding lock.
If you can
squeeze the rear tire and frame into one lock (I can sometimes do that with the folding lock) even better. Often I can't do this though because of the bigger tires and frame