I am willing to write a detailed tutorial on how to integrate GitLab CI with Gerrit providing a full-features code review workflow, based on how much interest is there on the topic.
If you’re interested please like this post, I’ll invest some time in writing the tutorial if I get enough likes.
I haven’t been using that setup in the latest years so I’m not sure they’re still working but you can surely use them as a starting point to achieve your goal.