It wasn’t the microwave, it was the ***dishwasher***!!!
I experienced the same issue with a beeping every 60 seconds. After several attempts to fix the microwave (unplugging/reboot/ mute function), I decided to completely remove the microwave from the kitchen and put it in my garage, then voila!!! The beeping continued, then I realized the issue was with the dishwasher, it wasn’t completely closed. It stopped beeping whenever I unplugged the dishwasher.
Ps. It’s a GE dishwasher, just like all other appliances in the house.
Hopefully this will help someone else with the same issue.