If your Android phone is running out of storage space, many phones will allow you to insert an SD card, which you can set as the phone's primary storage.

How to install Steam games to the SD card in your ROG Ally You can add another drive to Steam to create a shortcut for your Steam library. Follow the steps below to learn how.

However, SD Express cards are backward compatible, meaning they will function in your Android phone, albeit at reduced speeds. That is assuming, of course, you even have an SD card slot.