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,
Thanks,
Moritz