wget -O- https://updates.signal.org/desktop/apt/keys.asc | gpg --dearmor > signal-desktop-keyring.gpg su cat /scratch2/peter/Download/Linux/signal-desktop-keyring.gpg >> /usr/share/keyrings/signal-desktop-keyring.gpg
echo 'deb [arch=amd64 signed-by=/usr/share/keyrings/signal-desktop-keyring.gpg] https://updates.signal.org/desktop/apt xenial main' >> /etc/apt/sources.list.d/signal-xenial.list apt update
cd /tmp apt-get download signal-desktop=6.1.0 dpkg -i /tmp/signal-desktop_6.1.0_amd64.deb