There are two answers here, and one sits on top of the other. The first is whatever your provider has specified. Your provider may ask you to wear special shoes, a brace or a special cast. These devices take the pressure off the ulcer area. A prescribed device is not a shoe recommendation to be weighed against others.
The second is general advice. It exists because foot ulcers are partly caused by too much pressure on one part of your foot. Be sure to wear shoes that do not put a lot of pressure on only one part of your foot. Here’s what that means.
Wear shoes made of canvas, leather or suede. Do not wear shoes made of plastic or other materials that do not let air pass in and out of the shoe.
Wear shoes you can adjust easily: they should have laces, Velcro or buckles.
Wear shoes that fit properly and are not too tight. You may need a special shoe made to fit your foot.
Do not wear shoes with pointed or open toes, such as high heels, flip-flops or sandals.
Wear shoes at all times to protect your feet from injury. Check the inside of your shoes for stones, nails or rough areas before you put them on. That check matters more for you than it would for anyone else: you may not feel pressure from shoes that do not fit well, and blisters and sores can develop where the foot presses against the shoe.
One warning about buying: never buy shoes that are tight, not even if you think they will stretch as you wear them.