I'd go for Matrix, with Element or Schildichat (not the next gen versions for now) as clients. It's federated, which means you can choose which instance you want your account to reside on, end to end encrypted, has (video) calls, and some other features you wouldn't necessarily expect from others like spaces for groups with several group chats, prioritizing conversations (low, normal, high / favorite) and threads inside a conversation.
In the past there was some "Identity Management" server that was centralizing the accounts of matrix.org or any other instances, and it was managed by Vector which was an ONG or Company... Nowadays, I see no mention to it in documentation (at least from my quick overview) and vector.im redirects to element (matrix client). Did anything change? Do anyone know? The lack of transparency over Vector.im made me reluctant to recommend Matrix as a really federated alternative to messaging.
As far as I am aware the accounts for other servers were never centralised it was just part of the federation. If you search for a user the lookup queries your server then matrix or other servers it knows of. Unless thats just user search and not identity initially.
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.
If moving your family/friends is top priority matrix may be a bit of a learning curve.
In your shoes I would move to signal, and aside from some video playing bugs it works well and it is easy to use. Yes the privacy concerns are there, but that will be so for every app that becomes popular enough.
Canadian open-source peer-to-peer (i.e. no company-owned central server that might access communications) cross-platform software that does messages, voice, video etc:
Personally using Olvid with my friends and family but I guess it's only for very close connexions. Although I like it lot I doubt anyone else (more distant friends?) will download this app to contact me.
(It's free without the ability to initiate calls but everything else is here and works perfectly: groupchats, voice messages, sending photos)