There are several ways to solve this problem:
1. Cover the triangle with something a little bigger than the triangle and paint it the same color as the wall, so that the shape can be removed. You can even round the triangle with putty for decoration.
2. If the shelter is not allowed, you can hang the Eight Diagrams Mirror in the right place, that is, in front of your house. If you think it is too eye-catching, you can hang a small round mirror.
3. If the first two are not allowed, then paint this triangle into the wall color to make it look less obvious and weaken the influence on your home.
The above is for reference. Best wishes.