With regards to the above:

The CI dashboards offered by Gitlab EE (Ultimate) would still be insufficient for our needs from what I can tell in the documentation. We need to be able to see down to the job level to separate based on platform / checks failing, which isn't supported functionality. For this we will need to develop something different and custom, and unlike the previous iterations won't be able to make use ot Grafana (as Gitlab CI statuses just isn't something that fits well within the Prometheus/Grafana model)

With respect to dependency scanning, the core functionality is still available and the raw reports are published to Gitlab, what is missing is the visualisation (much like test reports on commits).

For issue boards, we've yet to fully do that migration - but when we do switch off Phabricator and bring it's content into Gitlab - we can definitely look at asking for bits and pieces of functionality to be moved over as Eike mentioned.

We were already successful in getting multiple boards moved over (for the project level).

I have plans surrounding MR assignees, watch this space....

Much like the rest of the people who have commented here, I agree with the philosophy of continuing to only use Open Source Software to develop Open Source Software.

Thanks,

Ben