GitLab team member here.

We've put a lot of effort into our integration with Jira. The docs [1] detail how it works and we have a blog [2] with some screenshots so you can see what it looks like in action.

What kind of troubles have you encountered?

1 - https://docs.gitlab.com/ee/integration/jira/

2 - https://about.gitlab.com/blog/2021/03/25/integrating-gitlab-...