FreeOTP+ is an free and open-sourced 2FA autenticator forked from the original FreeOTP with additional feature to help backup, restore and interoperate with other OTP authentication clients.

Additional feature:

Back up the data to Google Drive or other storage
Restore data from Google Drive or other storage
Material design and updated UI.
Android 6.0 on-demand permission support
Android 6.0 backup support. After reinstalling, all your saved authentications will come back.
Dark theme support
Search token

Source code: https://github.com/helloworld1/FreeOTPPlus
Original FreeOTP: here: https://play.google.com/store/apps/details?id=org.fedorahosted.freeotp&hl=en