SimpleX-Chat. It's not as streamlined as Signal for onboarding new users, aka convincing your friend and families. But most things work fine, chatting, calling and filesharing. It's completely anonymous, as in that you don't need to register with a phonenumber and or username. You can also self-host and use your own server if you are into that.
The more users it gets, the more investment it will have and become better. A fellow lemming also recommended Briar, but not familiar with it. Privacy enthusiasts also enjoy Matrix so also check that out.