Thanks for the questions, regarding decentralized support, there are two parts we think about, connecting teams and connecting channels.
Joining teams across Mattermost servers
In terms of managing authorization to join different Mattermost instances, you can setup individual Mattermost servers to authorize account and team creation based on GitLab SSO and/or a list of white-listed email domains, and later LDAP (Preview: LDAP/SSO support).
Joining channels across Mattermost teams and servers
In terms of connecting channels (some users think of channels as teams), our priority is offering the infrastructure and APIs to enable these scenarios, which have been raised by the community previously.
There’s three key steps to enable the synchronization of channels across Mattermost instances (and potentially Slack instances as well):
a) Mattermost ships incoming webhooks API (should be available in Oct 2 release, just waiting final review https://github.com/mattermost/platform/pull/715)
b) Mattermost ships outcoming API (https://mattermost.atlassian.net/browse/PLT-235)
c) Circle back with projects and companies like Slackline to discuss integration
Regarding encryption, it’s highly recommended that config setting options like STARTTLS be enabled, and to use additional modern protocols and standards (to be documented in detail along with config UI in admin console. Also, there’s additional work on OTR v2 being investigated.
Are there specific encryption scenarios you were looking for?