zehyani I would personally recommend against the Simple Mobile Tools apps for now, even though I've previously recommended them.
It seems that security vulnerabilities aren't taken seriously by their developer, so it doesn't exactly inspire confidence.
Google's app uses RCS, which means you can take advantage of encryption when the other person also uses it.
This of course shouldn't replace Signal, but it's at least an upgrade to regular SMS, which is completely unencrypted.