Hello, interesting to see how few sidewalks are mapped. I personnaly would also default to not adding the negative keys sidewalk=no, especially for rural roads where you could safely walk on the side of a wider road (not necessarily a shoulder..) or what I believe in English is called a verge.

Have you heard of Sidewalker it seems like you might enjoy that. Although, that tool shows all footways and not just sidewalks despite the name, and prefers separately mapped sidewalks to tags added to the road, wich I personnally am not a fan of… Although I understand separate mapping is better for accessibility as you can add surface, width and smoothness tags then…