It has been a long journey.
I have been gradually convincing my family, close relatives and friends to make the switch to Signal for over two years. I am already the "tech support guy" in all my circles so most didn't really question it. Most of my friends are quite tech-savvy, and some even did use Signal before I talked to them about it.
This also filtered out some "friends" who were never that close to me to begin with. So, that's a bonus, I guess.
Overall, my recommendation to others interested would be to tell people how much you don't like Meta's business model instead of the privacy aspect. I already ditched Facebook and Instagram many years ago, and this helped defend my point a bit better.
Well, some people called me paranoid and said "us regular people don't have anything to hide" when I told them how much data Meta collects about us. Of course, this frustrated me as my threat model is very small compared to most people here.
I explained how free services where instead the user is the product work, and how much I disagree with this model. I informed them that I use FOSS almost everywhere and that they exist for the greater good of humanity.