I’m only using the hosted version, it works. I do have a separate gitlab-runner in GCP at the moment though that is working fine.
If something doesn’t work for you I suggest creating a ticket?

All of what you said seems completely doable to me.

Primarily I want it to comment/annotate changes so peer review focusses on logic and warnings are clear.

You can. See https://docs.gitlab.com/ee/ci/variables/predefined_variables.html

CI_PIPELINE_SOURCE

How the pipeline was triggered. Can be push, web, schedule, api, external, chat, webide, merge_request_event, external_pull_request_event, parent_pipeline, trigger, or pipeline

You have full access to the API and can do whatever you want in the MR too.

I want the ability to specify multiple reusable pipelines, in a central place. This is not possible in cloud.

You can, with CI templates. Templates can be in a completely different repository

Lastly I would like to have multiple potential pipelines in a repository (e.g. smoke test and release).

I do have different pipelines for staging and production in my projects with no issue.

Ah yes this I agree. But it’s not like it’s different on GitHub. I guess I got confused because you said “Advantage of Github over Gitlab is code discoverability.”.
While no it’s the same? There is no advantage for GitHub

For example I think GitLabs CI is the worst on the market but if you integrate another CI you don’t have a means to feedback information into Gitlab.

You can do almost everything with the Gitlab API so I’m curious what issue you had.
I’m also not sure why “Gitlab CI is the worst on the market”? I really like in particular that I can have my own gitlab-runner on any machine.

You can use Gitlab exactly the same as GitHub though if you use the hosted Gitlab. I have multiple of my open source projects on Gitlab.com and everyone can access.