Lightroom mobile is a great idea. Photographs made on the iPhone automatically connect with desktop Lightroom, in theory. This is especially desirable since the new iPhone 7, via Lightroom, can make photos in DNG format.
I've read everything I could find from Adobe and LR gurus about the process, but I couldn't get the upload to happen with my system. Every instruction was followed precisely, repeatedly checked. Nothing.
Turns out, a Google search reveals lots of people with this problem. Lots of advice that doesn't produce the desired result.
The problem is bandwidth, folks. The upload doesn't happen directly to one's desktop or iPad. It is all processed via the cloud. If it doesn't get to Adobe's cloud site, it doesn't get to the desktop, even if the desktop is sitting next to the phone. It's easy to send photos directly via Airdrop, but the photos are first converted to jpg. If one has a slow internet connection, as I do with DSL, the phone always says it's syncing, but it never syncs. A reasonable broadband connection, via cable, and magically it happens, just like all the instructions say. But they never tell you it won't work without adequate bandwidth.
So, I live in a rather remote spot. Remote enough that the cable companies aren't interested, and DSL is the best I can do. The only way I can get the transfers to work is to visit friends with better internet. This considerably blunts the convenience of using the phone as a camera. For me, the process is way easier if I just use a camera and transfer the files via memory card.