When I moved this website to Digital Ocean on a fresh LEMP install I had an issue with the media that I had transferred over not appearing (in posts or in the media listing). I tried several things but couldn’t get it to work. When I tried uploading a new image I got an HTTP Error, which lead me to find this post > https://wordimpress.com/wordpress-nginx-http-error-on-image-uploader-fix/
After making the suggested change, I could successfully upload new images. I then re-ran the import and all the images finally appeared in the media listing and posts.