@Martin @nprofile1q... Yes, metadata could be reduced in
#xmpp but at least there is no single instance which gathers all the metadata like for centralized messengers
A well-designed centralised messenger such as Signal does not have access to most of the metadata that XMPP has.
Also the ability to run your own server helps to reduce the amount of metadata stored on strangers servers and increases digital sovereignty
This is quite misleading. The problem is that a lot of the metadata is visible to more than one server. Being able to run your own server doesn't help if someone else's server impacts your privacy. When Google Talk came along, they were hosting more than 50% of my contacts, so saw almost a huge amount of my metadata. Even though I was running my own server, Google saw more metadata from me than Signal sees with a centralised service.