wget -O- https://updates.signal.org/desktop/apt/keys.asc | gpg --dearmor > signal-desktop-keyring.gpg;
cat signal-desktop-keyring.gpg | sudo tee /usr/share/keyrings/signal-desktop-keyring.gpg > /dev/null

wget -O signal-desktop.sources https://updates.signal.org/static/desktop/apt/signal-desktop.sources;
cat signal-desktop.sources | sudo tee /etc/apt/sources.list.d/signal-desktop.sources > /dev/null

sudo apt update && sudo apt install signal-desktop