If you care about freedom, you shouldn't use #Signal. If you care about security it might still be your best bet, though take a look at briar it might (even better) cover your needs in that case: https://briarproject.org/
Here's two articles which together shine a pretty good light why I don't consider a useful option:
* https://matrix.org/blog/2020/01/02/on-privacy-versus-freedom
* https://drewdevault.com/2018/08/08/Signal.html
1/2
One example about this freedom aspect:
The #Signal Android app as distributed by OpenWhisperSystems contains nonfree libraries by google so is in essence nonfree.
In addition OWS forbids anyone else distributing a Signal client which removes these dependencies, threatening legal action (with Trademark Law, etc.).
The remaining options are:
* Maintain and build a fork for yourself
* Rely on one of the projects that ignore Moxie's threats and distribute a free version of signal anyway.