From what I say is that the GitLab dependency is really a setback. It is a dependency that must be managed. GitLab has more dependencies on its own. One is Go, another is Ruby - and yes, this is irritating.
So, from a real use case, Zulip and Let's Chat start to look better alternatives as they do not have a BIG dependency just to have an OAuth feature for example.
This is a little sad, hope that this will change in near future.