I followed the guidance here to do a FreeOTP backup with adb backup -f <backup path> org.fedorahosted.freeotp. After I wiped my phone and tried to do an `adb restore I get the message "Now unlock your device and confirm the restore operation." but nothing on my phone happens or prompts, nor does FreeOTP have any keys installed.
I am on Android 8.1 with adb 1.0.32 on Ubuntu 14.04.
I guess the adb from sudo apt-get install android-tools-adb was a bit too out of date. I downloaded the latest version from https://developer.android.com/studio/releases/platform-tools.html and extracted just the adb command, which is Android Debug Bridge version 1.0.39 Version 0.0.1-4500957, ran it and my phone prompted for a "full restore" which sounds scary but in the end just did a full restore of the FreeOTP. After it was done I have my keys back, yay!
adb to the latest version doesn't seem like a reliable way to fix. It seems like I read somewhere that the version of adb on your desktop is supposed to match the version of Android on your device. And that there's a backward incompatibility after 1.0.39. I don't know.
Commented
Aug 6, 2018 at 7:43
the new version (Jan 2023) of freeOTP allows backup and restore within the app. it updated automatically from the old version via google playstore.
https://play.google.com/store/apps/details?id=org.fedorahosted.freeotp
when you open the upgraded app for the first time you need to chose a password to encrypt the backup.
Attention: to restore from backup (e.g. on another device), it is required to use freeOTP/restore and there enable settings/display advanced devices and then navigate to the backup file 'externalBackup'
without advanced devices enabled, the app doesn't see the file externalBackup
