I moved 10 of my non-IT (male, age ~30-35) friends from FB Messenger group chat to Signal. None of them had any problems setting it up, none had any questions during the setup. I just invited them to the group after they created accounts (you can also use an invitation link) and the chat continued on Signal. No one has looked back at FB Messenger and we are not missing any functionality. I am slowly spreading in my circles and so far with only positive feedback.