Here is an infographic from the national association of Realtors that shows the impact of remodeling projects from a home buyer’s point of view. There are two categories, “joy” and “return on investment”. The projects with high “Joy” scores attract buyers.
Painting the front door in a primary color will also increase joy assuming it doesn’t clash with the rest of the house. A new backsplash in the kitchen falls into that category as well. Door locks that have keypads or that can be controlled by apps on a smartphone definitely spark joy.
If you plan to sell your house I always recommend cleaning, decluttering and painting as the obvious least expensive ways to increase salability.