On both iOS and Adroid (iPhone 7, and GPixel 3a) if I have over 50+ photos in my Lr library, it takes minutes if not longer to open the Lr app. That might be low storage space causing it to freeze, in which case could you give a prompt offering to wait to load photos or load just a few? It might also be though that these file can really add up if there's hundreds of them and just physically moving it all to the RAM takes a long time.
But above all else, I wish Lr Mobile didn't even think about loading the photo library until the camera was fully loaded because those Kodak moments don't wait for your app to load. I've lost some really good shots waiting for Lr to start up so I have to choose between keeping almost no photos in my library or not using the camera.