The current GitLab Runner metrics included in the GitLab exporter are quite basic. There are 3rd party exporters offering more metrics.

The biggest projects seems to be https://github.com/mvisonneau/gitlab-ci-pipelines-exporter. This project offers a dedicated exporter written in Go and a grafana dashboard.

Here is a complete list of all new metrics: https://github.com/mvisonneau/gitlab-ci-pipelines-exporter/blob/main/docs/metrics.md
The exporter offers for example the branch name as labels in the metrics, which can be useful for some more alerting for Trusted Runners (for example in T346307).

We should review this or other exporters and evaluate if it makes sense to add this exporter to our GitLab stack as well.