Signal is a nice suggestion but is based in the US meaning they could be subpoenaed and legally not allowed to say. It’s unlikely you’d be targeted though, unless you’re a very high-profile person. If you’re concerned about where servers are being run and who by then matrix is a great alternative.
I recently did a very simple PR for this, adding keywords so I don’t keep forgetting the name of the app and not being able to find it 😅