I don't lock my regular bike because I don't leave it unattended while shopping, working, etc.
On the occasions when I've ridden a cargo bike to Walmart or wherever, I just used a good U-lock and locked it to one of the cart corrals.
If I was going to improve on that, it'd just be a matter of using two U-locks instead of one or something like that.
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"be careful this rando stuff is addictive and dan's the 'pusher'."