I didn’t really have a hard time installing Omeka as a subdomain, however, I downloaded the Omeka S version first. I read the reflection of a classmate saying they accidentally made the mistake of downloading the S version and I realized I did the same thing.
Another issue I had was when I was trying to upload pictures, one of them was not working and I realized it was because the format was an HEIC image not a jpg. I then had to figure out how to have these images show up on a site. It was easier to upload images onto the Omeka classic version than the Omeka S version.