In Mattermost v6.0+, language support differs across products in the suite. Language support parity across the suite is coming in a future release, but currently language support for Channels and Boards are handled separately.
Set your preferred language
Channels language support
To configure Mattermost to display in a supported language, select the gear icon and then Account Settings > Display > Language. This setting applies only to Channels.
Boards language support
From Mattermost v6.0+, select the gear icon in Boards and choose Select language, then select your preferred language from the list.
Playbooks language support
Playbooks is not yet localized into supported languages.
How complete are translations?
You can view the progress of each translation here:
How can I help?
If you're interested in contributing to translations you can: