OK, nobody here does Lightroom Mobile on Android. So I wasted considerable time getting self taught. Al least now I know why nobody does it. It really sucks.
First step, I had to install an Android 3rd party file manager to copy from a camera card reader to the Android device. The native Android file manager can't do it. Then another 3rd party app to rename the files on the Android device. Couldn't find a file manager to do both.
Then I had to select the renamed raw files using the 3rd party file manager, and "Share" them with Lightroom. That's how import works. You can't import inside Lightroom. The direct "add" function in Lightroom Mobile won't look anywhere but the Gallery. It seems Lightroom Mobile is focused only on images you take with the device that go straight to Gallery.
But then the kiss-of-death. Lightroom Mobile copies the full sized original raw files to the cloud. It won't use the raw files on the Andriod device like Lightroom Classic does on Windows. I guess a should not have been surprised by that, but I was. Naivety on my part. Not too bad at home with my fast Wifi and gigabit internet, but imagine doing that in a motel in Bum Stop, Montana, or Snowera, Italy. And image doing that on a 2 to 3 week trip, 200+ raw files a day from a 50 megapixel full-frame camera. Probably blow through Adobe's 20 Gig freebe cloud storage pretty quick, while a 128 gig SD card in the Android gets wasted.
I gave up before I tried to figure out how to transfer everything from Android to Windows back home. But I suspect that can't be done. I expected to move the catalog, move the raw files, open the catalog in Lightroom Classic and link it to the raw files. I don't see a Lightroom "catalog" anywhere on Android or in the cloud.