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.
Please also note that you don't have to install GitLab itself on Kubernetes in order to add a Kubernetes cluster to your projects or groups. We updated the docs yesterday to prevent confusion about this https://gitlab.com/charts/gitlab/merge_requests/599/diffs
We had multiple ways of installing on Kubernetes before but we reduced it to one canonical helm chart https://docs.gitlab.com/ee/install/kubernetes/gitlab_chart.h...