How to bring footage in without uploading from the phone — and what Apple does not allow.
Put the clips in a folder, share it as “anyone with the link”, and paste the link into the Drive field in step 1. Relsko downloads the files into your project.
In the Photos app select the videos, tap Share and choose “Copy iCloud Link”. This creates a public shared album; paste the link (share.icloud.com/photos/…) into the iCloud field. Newer “photos.icloud.com/shared/album” links cannot be downloaded automatically — Apple blocks them — so use the classic shared link or upload directly from the phone.
Apple does not offer a web API for iCloud Photos. Sign in with Apple only verifies identity and gives no access to photos. Shared links are the only way to bring iCloud content into a web app. Google Photos offers a picker; if you need that flow, tell us.