Gitlab SSO doesn't work when joining public teams

No. I've tried with many users, and in all cases:

1. They already have an account on Gitlab;
2. They don't have an account on Mattermost;
3. There is no account on Mattermost with the same email address as the user on Gitlab.

By the way, I also tried to first create a team using the Gitlab account (wondering if could be a problem related to user creation and logging at the same time) and afterwards trying to enter a public Team, but the problem persists. In summary, users logged from Gitlab SSO cannot join public Teams.