tl;dr: looking for suggestions for new instant messenger (WhatsApp, Telegram, etc.)

so I used to use Facebook Messenger a LOT, actually much more than even texting (I know I know, Facebook=spyware lol). I wanna ditch Facebook so bad but most of the people I talk to, I message through Messenger, and thus, I don't have most people's actual phone number. so I'm looking for suggestions for a new messaging platform, where these are my priorities:
1. Ease of use/existing userbase (e.g. the more of my friends that are already on it, the better)
2. Security & Privacy
3. the ability to easily find people I know without having their phone number