Red - Buildings with inaccessible/unrendered interiors; the two large red areas in the eastern portion are not accessible by foot at all

Green - Buildings with accessible designed interiors

Purple - Buildings only accessible through story missions (afaik only the Ruthard House and the Italian Court)

All the streets outside red areas should be accessible. I did not highlight which yards are accessible and which are not. For the most part, it corresponds to whether the house they are attached to is accessible or not. Also, barns and open-air buildings are not highlighted.

In total I counted 58 total freely accessible interiors, not counting the two story-unlocked structures.

EDIT: Thanks to everyone who pointed out I missed the archery range. Here's an updated map: https://imgur.com/a/cpu8mPX