Signal only provides a script for .deb based distros on their official website. The flatpak is currently not ideal because it stores encryption keys in plaintext.
The provided link suggests an automated installation in a Ubuntu Distrobox including automated updates. Useful for every distro that does not natively support .deb packages.
i mean its great if it works well, but kinda funny we need to run a full distro in a container to run a browser to run an IM program