If you want a simpler solution than Matrix and don't mind using a non-opensource app you could try twinme. You only need a username and a picture to create an account (could be anything, "Jane Doe" and a white square if you want). It has a couple unique features like multiple identities and click-to-call links, which you can share with people who don't have the app so they can call you using only a web browser (e.g. on craigslist, lost pet flyers, ...).

I work on this app as a full-stack dev, and for what it's worth we only upload/store data that is strictly required for the app to work. We're lobbying to open source it because we have nothing to hide and we know how important it is for the privacy/security minded folks, but it will take some convincing before management agrees to it...