Use USB Serial to communicate with Circuit Python boards. You can use it to see the print() outputs for debugging, or enter the REPL to execute python commands on the board. Using the REPL we can read and write the code.py and other files stored on the board that would be inaccessible due to file storage incompatibility on Android.
See the Hackaday.io project page for more: https://hackaday.io/project/162561-android-circuit-python-editor
WARNING: This app is in the alpha stage, it may not work at all for you. Or worse it may work improperly and erase, or overwrite with non-sense the code on your board. Please keep an extra copy of any important code stored on your PC or somewhere other than the Circuit Python board. That way you can always remount to read-only and save your working code on the board using the standard USB Storage file transfer method.