The Signal client for desktop is a really bad example of free software. It does techically have a free license (or better say a jungle of components with various free licenses), but it is almost impossible to build it yourself. There is a reason why Debian does not have its own builds.
Even the Flatpak people gave up on it. They are downloading the binary deb package from Signal and unpacking it. I am not kidding you. Regards Stephan
