Support for RBAC for GitLab Managed Apps was added in 11.4 [1]. You can also connect any Kubernetes cluster hosted anywhere - see the docs on that [2].
What problems are you hitting when installing GitLab on Kubernetes? You can always open an issue about it so it can be prioritized for fixing.
[1] - https://gitlab.com/gitlab-org/gitlab-ce/issues/29398
[2] - https://docs.gitlab.com/ee/user/project/clusters/#adding-an-...