Mattermost Plugin Gitlab - Needs to be manually configured?

Do I need to manually configure the Mattermost Plugin for Gitlab as an OAuth application?

I am a little confused about the integration state of the Mattermost Plugin Gitlab - I could activate it from the Marketplace (although I first thought it should be already activated), but now I would need to configure it in the System Console as a GitLab OAuth app. That seems a little weird to me, since Mattermost is of course already configured for Login purposes.
Is this still correct and I need to create another OAuth app for the Plugin? Or did some misconfiguration happen in omnibus while upgrading trough the years?

Hope someone can help or share their experiences,