Anyone have any idea how to protect glass door from dog scratch?

I’m going to assume this is a sliding door.

I would try buying an inexpensive (or trash pick) a lightweight window screen and quality double-face tape it to the lower part of the door. Or there’s always exterior Velcro.

Either screening, or vinyl/clear polycarbonate sheet cut to size, and there’s the decorative metal that folks use to face radiator covers (Lowe’s).

Perhaps after a bit it will break him of the habit.

Given that you don't plan on training your dog not to jump or scratch the door, you could try a hard plastic panel across the glass. The panels are usually in the area where they sell screens. You can use commercial grade velcro strips to keep it in place. Hope that helps.

If the dog is allowed in and out of the house, there are doggy doors that work with sliding doors. My sister actually trained her dogs to ring a bell that she hung from the door knob so they could let her know they wanted in or out. This only works because she actually comes and opens the door for them, though. (I would not personally provide this level of service!) If the dog doesn't come inside, you may need to go outside more. Usually this behavior comes from wanting to be with you.

I don't think anyone here effectively answered the question. I'm also on the hunt for scratch protection for my sliding glass door. I'm looking to probably go the 3M clear paint protection route for my small dogs. It's designed to be durable, perfectly clear and not damage paint when removed. I'm hoping it will work on glass too.

Training your dog is the only long-term solution, OP.

I love my dog so much but it constantly did the things that irked me most. It would chew on things that it shouldn’t or jump up and down out of the blue. Whenever I put on the leash, it would pull on it. Whenever it was out of the house, it would continue digging on the ground - I wish I could tell what it was looking for down there. All the things it did left me feeling depressed as if I failed it monumentally.

But since I discovered Brain Training for Dogs and applied the system offered, it now behaves the way a beautiful dog I always expect of.