I‘ve built https://github.com/dx-tooling/productbuilding-orchestration for more or less the same use case as Broccoli, but in my case a) the „frontend“ is Slack, not a ticket system (but the agent people talk to in Slack manages the ticket system under the hood), and b) everytime there is a new commit on a PR, a preview system is bootstrapped or updated, and the codebase that is to be previewed explains how it wants to be deployed for preview.
This works really well.