We have had kids with two very nice bikes at urban universities (bad bike theft problem) for two undergraduate degrees and two graduate degrees for a total of 18 years total. Neither bike has been stolen or attempted to be stolen. It's not complicated - the whole idea is to make it hard to get the parts off and to make it far more convenient to mess with someone else first. And it works as evidenced by out track record. That said, it's not unlikely that an e-mtb presents a different problem.

• Seat, handlebars, skewers were all secured with Pit Locks.
• U locks were used for stops during the day and classes. A U-lock and a chain lock were used when they were locked outside at night. This requires two different sets of tools to defeat.
• Always attempted to lock them next to a bike that was either flashier or locked poorly.
• Never lock the bike all by itself. This blows the convenience factor because there's nothing easier, there's just your bike.

For an e-bike in todays urban environment, I'm not sure you could secure it adequately for longer than a short stop to pick up something. But the same pit lock and locking strategy would apply. Because you have assist, then you can carry the biggest baddest locks around. The problem though is all the parts that are accessible and can't be really locked down. I'd also add an alarm. They're cheap on amazon and it couldn't hurt. Finally, get good insurance and then rest easy. If it gets stolen, you'll get paid to get a newer higher tech version.

J.