Clone this repository for each Signal account, for example:

git clone https://github.com/cyrus-and/signal-desktop-docker my-signal-account

To import existing Signal Desktop data put it in the Signal directory, otherwise it will start from scratch, for example:

cp -r ~/.config/Signal/ .

Just run make to start Signal Desktop.

Use make build to rebuild the image in order to perform a system upgrade (if really needed), make clean-docker to remove everything Docker-wise and make clean-signal to remove everything Signal-wise (use it with care).

Use the gpg-export.sh utility to save the whole directory as a GPG encrypted archive:

./gpg-export.sh /path/to/backup/