#Solution 1: Manual Uploading/Tracking to Files.app If you want to stick to iCloud Drive and achieve the this, you'll need to manually upload your photos to iCloud using Photos -> Select -> (Select Photos) -> Share -> Save to Files
In this method you'll have to manually keep track of the photos you've uploaded and the new ones that haven't been uploaded yet.
#Solution 2: Google Photos for iOS Google photos app for iOS brings the same
Free Photo and Video Storage
feature for iOS, which were initially advertised with the Google Pixel.
In this method, the app handles the sync history and keeps track of the backup metadata for you, so you won't have to worry about uploading new photos manually.