Is there a general term for photos that don’t include people?

There isn’t a general photography term meaning “not portraits” or “photos without people.” In practice, photographs are described by what they are of, not by what they exclude. For example, images might be called landscape, wildlife, architecture, still life, street, macro, or documentary depending on the subject and style.

Also, “portrait” can refer to both a subject/style and an image orientation, while “landscape” is also commonly used for orientation. If a photo includes people but isn’t posed like a traditional portrait, it may be described as candid.

So the best label for your work is usually the specific genre or subject matter rather than a catch-all term for “no people.”