I don’t know the state of the Android viewer app, but wonder whether the improvements in sharing models would let your clients view your models in a browser?
Try this link on your older Android device, and see if my train shows up:
I am trying on an old Android phone as well, and it is taking the page a long time to load!
I went back to my old Android phone some time later, and sure enough I could view my train in Chrome.
Later I realized that people only use phones to run the viewer apps. The share link I gave works in desktop computers. Your clients could view your model without having to install a mobile app.