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.
Flatpak signal can integrate with kwallet and gnome keyring, so unless I’m missing something, you’re wrong.
Yeah, I have been using it like that for a while. It is just a single environment variable.