Ability to have structured/semantic "related bugs"?
Does GitLab have something similar to Bugzilla's "external trackers" or Launchpad's "also affects" - semantic linking to issues on other trackers (and other tracker platforms - not sure if BZ can do that?)?
A link to an external bug in a comment isn't "understood" as a bug by GitLab (so e.g. it can't list it before comments under "external bugs", can't separate out its ID in that tracker, can't show its state (status, last modified etc.)
See for example the top of https://bugzilla.redhat.com/show_bug.cgi?id=1462381
It seems like GitLab is doing EE/CE differentiation even on stuff like internal related bugs; see https://gitlab.com/gitlab-org/gitlab-ce/issues/4058 and https://gitlab.com/gitlab-org/gitlab-ee/issues/2001 - there's a chance foreign-platform issue comprehension will grow out of that EE feature if it doesn't exist at the moment.
I suspect this will be an ongoing structural problem with the use of an open core product like GitLab unfortunately.