Not really tools, but the most effective way really is to do it for them. Most people who don't really care whether an app they use is open source or not won't care about what you say either, no matter how much you try to explain. My wife didn't really care about using linux, but when I actually installed it on a spare laptop and let her use it, she adapted just fine. I installed Firefox Focus on her phone and now she uses it for quick browsing. Same with Signal for my family. I asked my brother to install it on our parents' phones and now they use it for all family group chats.