Take the door off the hinges and then remove the lock from the door. I guess.

I had to do something similar years ago with the door that separated the kitchen from the garage. It’s been years since it happened so I can’t remember all the details but I think the deadbolt was sticking and I decided to clean it and oil it. So I took apart the lock (easy to do), cleaned it, lubricated it and put it back together (not as easy to do). I remember the deadbolt was stuck in the locked position. DAMMIT. I was in the kitchen and the hinges were on the other side of the door. So I went through the front door and then through the big garage door in order to get to the other side of the kitchen door and pop the door off the hinges. That was fun. At the very least I learned how to put a dead bolt lock together properly.

After I relaxed from that little mis-adventure I realized how insecure my kitchen door was, despite the deadbolt. If the idea of the deadbolt was to keep invaders from getting into my house from the garage, the hinges are on the WRONG SIDE OF THE DOOR. Sigh.