How is it possible, that Signal still only provides a .deb package and no .rpm, or even better AppImage or Flatpak? There is an unofficial Flatpak but is it secure?
OP, what distro are you running? You mention a whole bunch of package formats they don’t provide, but never mention what format you require. Depending on the distro, making a build script (or converting the .deb) really isn’t Rocket Surgery ™.
Signal aims to be the messenger you can tell your grandma to use. To live up to that promise they have to provide more packages.