I really wonder why there is no .rpm file, only a .deb file to download from the
official signal site (as far as Linux distros are concerned.) signal download for Linux
FWIW, there is a community maintained Flatpak version, which works on Fedora.
For GNOME users there is also a promising new unofficial client called Flare. Currently still missing some core functionalities such as calling, bot works well for text messages.
A better question might be who else is auditing the code.
Signal’s stance on Websocket/GCM years ago would have me a little skeptical of any packages not directly coming from them. Signal can afford to be picky somehow, while others offer encrypted chat fine (Keybase builds RPMs and deb).