My dad has neuropathy, also a defibrillator can he use a foot massager

First, ask his cardiologist. There are remaining myths about what affects a pacemaker and a pacemaker/defibrillator. I had a pacemaker/implanted cardiac defibrillator from 2010-2017. On the door of our nurse break room, it stated beware of microwave if you have a pacemaker. 🤔
Cell phones, microwaves, even airport screenings……not true. Just mention the pacemaker before going through security. MRI imaging is a no-no, although I’ve read some newer pacemakers are MRI compliant.
Strong magnets are used during surgery to turn the defibrillator off temporarily.
I now have a pacemaker only, a biventricular pacemaker specifically. Just this month, I ordered a back massager for my chair. It warns not to use if you have a pacemaker. Nonsense. Common sense says you would not put anything electrical/magnetic directly on the area of the pacemaker.
Again, ask the cardiac electrophysiologist who did the surgery.
*A good foot massage with a menthol component is what I use on my feet. I don’t have much pain, but claw toes(?) that are very uncomfortable and just a general tight feeling around the feet. I do use an electric foot massager regularly but can only use it on the lowest setting or it actually causes pain.

A foot massager will not harm your dad’s feet or his heart. It might make his feet feel good but doubtful it will have any curative effect from PN. As you can see from the number of posts about PN we’re all looking for a miracle cure. At this time I don’t believe anything exists that “fixes” PN problems being it pain, numbness, cold or hot feet. Good luck and good wishes for your dad.