Getting Your Mattermost Community Login and Password
Our ZeroTier Central at my.zerotier.com has a Community tab that simply frames an instance of Mattermost, an open-source Slack alternative.

Mattermost has native desktop and mobile apps. If you want to use those, you'll need to obtain your Mattermost password from Central. You can do this by logging into Central and then going to my.zerotier.com/api/status. This will give you a JSON object that contains among other things your community login information. This is found in the communityEmbedLogin field under login_id and password. (You can't change this password. It's for Mattermost and is generated and synced by Central.)

Once you have these credentials you can install the Mattermost native apps and point them to https://community.zerotier.com/ as their Mattermost instance URL. You can also go there and log into Mattermost directly in a web browser instead of accessing it through Central.