There are big wishes for Signal to adopt the perfectly working Flatpak.
This will make Signal show up in the verified subsection of Flathub, it will improve trust, allow a central place for bug reports and support and ease maintenance.
Flatpak works on pretty much all Distros, including the ones covered by their current “Linux = Ubuntu” .deb repo.
To make a good decision, we need to have some statistics about who uses which package.
So… not using Signal because it’s based off a conspiracy theory that it’s secretly funded by CIA?
Well, let’s stop using RSA and encryption because the most used secure crypto algorithms today were created by none other than the NSA!
EDIT: None of the alternatives provided are good alternatives for Signal. Matrix is an extremely complicated protocol that lacks some features compared to normal IM apps (I use Matrix and the experience is quite close to a standard messaging app). XMPP is dead and has a very niche userbase. The others are not suitable for being a daily messaging app.
Signal is a good alternative and while I do agree with some points, they are not bad enough to prevent you from using it (e.g. not having usernames).