Reminder: Any AO3 apps you might find in your app store of choice are unofficial and not supported by us.

ao3org:

The Archive does not currently have a standalone mobile app available for download in any app store. If a third-party app or website requests your AO3 login information, please proceed cautiously and be aware that you are doing so at your own risk. While there are no known security issues at this time, you should always change your password if for any reason you believe your account may have been compromised.

All current information regarding AO3 and mobile apps is available in our app tag.