Been using Telegram for a long time. I don't trust it any more than I do with WhatsApp (therefore, Facebook), however it is well done and thought out, has a real desktop client with a real desktop UI toolkit and enough of my contacts are on it already, therefore it's the best compromise to me. I greatly dislike Signal's UI when I tried it out and I've read about some weird decisions lately (that "using a PIN? uploading to cloud" debacle some time ago). I also believe it shouldn't require a phone number if its focus is privacy and security. Matrix would be my go to in concept, but its userbase is even smaller. At the same time, alas, I am forced to keep using WhatsApp because "everyone" is on it, and if you aren't, you're going to miss out, be it parents school chats, work groups, less tech-savvy friends, parents..