hi @alexjironkin,
Mattermost Beta2 will include production install instructions, along with new admin tools both for web and command line, draft is here: Mattermost Beta1 Production Install
GitLab Mattermost SSO configuration instructions can be found here: https://github.com/mattermost/platform/blob/master/doc/integrations/sso/gitlab-sso.md
The omnibus config settings would be the recommended deployment (e.g. require GitLab SSO for team creation, disable creation of teams from email accounts by default, etc.).
We’d recommend taking the GitLab Mattermost bits from the omnibus (rather than the latest Mattermost bits), because the config settings in omnibus will apply to that version specifically.
Please let us know if these work?