By "cloud photos" do you mean the syncing of the collections from your hard drive to the Adobe servers? If, yes, you can turn off the sync by clicking on the name plate in the upper left corner of the program.
Keep in mind that there are two versions of Lightroom.
Lightroom uses cloud storage and Lightroom Classic stores images locally.
Lightroom does have an option to store files locally along with the cloud, but you cannot turn off the cloud storage. Along the same lines, if you are using Lightroom Classic you can enable cloud storage, but the program is desktop based.