Place your Android device in Developer Mode: Go to settings > About Phone> and tap on this several consecutive times (maybe 5) You’ll see a note stating developer options have been enabled.
Or complaints about the fact there is nothing for the server to connect to. If so, the Android is connected as PTP and needs to be changed.
Now the two devices are connected.
You can change “my-android-backup” to anything you wish, just insure the file extension is adb.
You will be asked to create an encrypted file, if your device is not already encrypted, just type in a password you will remember!
If your device is already encrypted, you will be required to encrypt the backup.
The backup time will depend obviously how much you have ‘collected’ on your device, with no real vision of progress, so chill and leave it alone. ADB will quit when done.