I really really want this to work, but it doesn't, at least on iPhones. The sync only seems to work while the app is open, it uploads JPEG instead of HEIC, and videos aren't uploaded at all.
I would be happy to pay money to make this work properly.
In the meantime, I pay extra for Google Photos (for display/search/tagging) and iCloud (for reliable auto backup) and need to find a way to automatically download the iCloud things to my Plex/NAS machine.