How can I sync my iOS (in my current case, an iPhone8) photos+videos to both iCloud and Google Photos but delete all the photos+videos from my iOS device, primarily to free storage space (on my iPhone)?
Details and (known?) problems
This answer suggests that I can not do this, because deletion of photo/video files from the iOS device also deletes it from iCloud (example scenario below), which violates my goal. However, I'm hoping there's some workaround.
Specifically, I want to "free up space on my device" like I've done several times previously with Google Photos (GP). However, the GP photo/video file deletion may effectively delete the same photo/video file(s) from iCloud–which is what I'm trying to avoid.
Best Answer
The following worked for me. For my current purposes, 'iOS device' = iPhone8 running iOS 11.4.1.
Procedure:
Permanently delete photos from Photos.app on iOS device; excerpt:
Delete photos permanently
If you want to permanently delete your photos or videos within 30 days, you can remove them from the Recently Deleted album. When you delete a photo from this album, you can't get it back. (An aside: this procedure can be quite cumbersome for thousands or more of photos+videos.)
Reactivate iCloud Photo Library.