I chose the option to change the data to SD card on my Android. Since then the app only shows this page and does not comes out of it. I've already turned on and off my phone, closed the app, waited more than 30 minutes on this page but it doesn't come out. What should I do?
You've posted in the forum for Lightroom Classic, the traditional folder-based version of Lightroom. You'll get better help more quickly if you repost in the forum for the Lightroom Cloud (mobile) versions of Lightroom:
This was an issue in 6.4 if you switched the storage location before the sync had completed. It has been fixed in 7.0. Updating your app to the latest version will fix it. The workaround is to switch back to the original storage location and wait until the cloud sync completes, then switch to the new storage location.