From a teenager's perspective, Instagram and TikTok are a lot worse for your mental health than say, Snapchat and iMessage.
In addition, for the queer community example - I'd say the perfect parallel for today would be Discord. Anyone can find a community and make friends on Discord, but it's probably not 5% as damaging to mental health because it's a communication based platform
Matrix is the holy grail of chat. It's end-to-end encrypted by default, federated and open source. The only problem is that not a single one of my friends or family was on it! Luckily the Matrix folks had already envisioned a solution to this problem - they built an API enabling 'bridges' between Matrix and other chat networks. This struck a chord with me, maybe we could finally build a single app that I could use to chat with all my friends, regardless of which chat app they used. Through the Matrix community I met Tulir, the most prolific bridge developer and we started working together on what would become Beeper. I've been using it as my primary chat client for almost 2 years now. I could not imagine going back to the hot mess of 12 different chat apps I had before!
Beeper is a paid service because I think it aligns interests between us and our users. We make a featureful and secure app, in exchange you pay us money. For those who prefer to self-host, you can run the entire Beeper backend stack on your own server. The vast majority of the code we've written for Beeper is open source on gitlab.com/nova. Our desktop client is closed source, but you can use Element (or any open source Matrix client) if you prefer. See our FAQ for more info or I'd be happy to explain more.