https://flathub.org/apps/details/org.signal.Signal
I wish Signal would officially adopt the Flatpak and AppImage versions. They are pretty widely used and depend on third-party build pipelines right now, which is a risk.
The other messengers with the same amount of funding can do it and it's not a great amount of work, with the community being able to contribute to build scripts.
Snaps, yes definitely, but mostly when there is a UI involved.
I tend to prefer Flatpaks for apps with a UI.
Snaps would have been good for CLI apps if Canonical would just give it a rest already, and allow them to be decentralized and stop pushing them so hard as if that would make us use them.
So while I do sometimes use snap packages, I'd prefer not to.