You're right, I forgot, in that regard for example with xmpp, besides being able to self-host you have multiple services, perhaps eventually there might be non just simpleX services but hosted by others as well, though it seems whether simpleX or self-host for now. So it's true it's decentralized by definition, perhaps not so much in practice though.

There's another sad thing I just remember, it doesn't yet support multi-divice syncing, and the alternative is to create groups with different members, one per device, and then in the same group apply the same for all other multi-device members. The reaction so far from the devs is that it's not so important having a workaround at hand. So both things made me drop my trials with simpleX...