This question was asked and answered multiple times. The answer was: there isn't a workflow that works like this. Tell me what I've misunderstood:
Photos can use referenced files. The files are not stored in the Photos database. Edit directions, edited versions, and thumbnails are stored in the Photos database.
Lightroom uses referenced files. It can store the edit directions in the original file, but stores other information in its database.
So, while I can see no way to share the edits between the two programs, it seems like the file can be shared. I'm unaware if adding LR edit directions to the xmp data in the original file will make that file unusable to Apple.