Transfer Signal using Signal-native Backup and Restore

The best source to install Signal is always direct from the website https://signal.org/android/apk/#target 

Export on the old phone

Open the Signal app and go to the settings. Navigate to Chats and then Backups (at the bottom). If they are disabled, turn them on.

Note down the passphrase, you'll need it for the restoration!

Data transfer

Import on the new phone

Starting Signal the first time, it asks you if you want to set it up newly or restore from a backup.

On the next screen you will be asked if to restore from another device or from a file. Chose the latter:

On the next screen click the button "Choose backup":

This opens the native Android file chooser. With the button top left you can switch between internal storage and memory card.

Choose your backup file.

The next screen will show you a few meta information on the file (age, size):

Tapping on "Restore backup" will ask you for the passphrase:

Now, the restoration is in progress:

Guide to be continued.....