As far as I know, anything that does not need a property release, model releases (people can be recognised by their face for example),
cars can be a problem, general landscapes seem to be ok, but some national parks require a release - you have to check that out for yourself, and of course you have to be the author of your work (photo).
Adobe will reject the photo if they think some release is required - but don't send in buildings that are owned by someone/company, inside a company, office room and so on. These will require a release!
Read the material that you can find at the top of the Adobe Stock Contributors page. Relevant info is there!