Matrix.org is centralized like Signal (you can say Matrix is not centralized on paper, but in practice this isn’t remotely true). Both are stockpiling metadata in the West… what’s worse is Matrix’s eventual consistency model means syncing metadata to all servers is a by-design requirement (& also why all servers & clients are slow). There are options like Snikket to take all the hard parts of self-hosting out of the equation, but finding someone you can trust to host a server might be worthwhile. I would be wary of anything centralized.