Delete Photos from Lr on iPhone

If you delete an image from the LrMobile app, it is not deleted from your sync-enabled Lightroom Classic catalog. What does happen in LrC, however, is that the image is "unsynced" in LrC so that it will be removed from the All Synced Photographs special collection and from any synced collection that it may have been in. It is, however, still in the catalog and can be found still in the original folder (and in any unsynced collections that it may be in).

If locating images in LrC after deleting from the LrM app is a problem for you, an alternative workflow could be not to delete from LrM, instead flag the images as rejected. That reject flag syncs to LrC, so you could then select the All Synced Photographs special collection, filter for rejected items, then select them and remove them from that special collection (which automatically deletes them from the cloud), after first making sure you'll be able to find them again in the LrC catalog. The reject flags would still be applied, so remember to remove them.