I see someone request a system that they can use to replace Jira in Notion almost every day so I collaborated with the CTO of the startup that I work for to create this template. Needless to say, this isn't a full Jira replacement but we were able to replicate a lot of the core structure. You'll have everything that you need here to get up and running, and it'll serve as a solid foundation for you to build on. The beauty of managing your workflow in Notion of course, is that you can customise far more of this system compared to Jira.
I've found that adding this to our workspace has given the rest of the business much better visibility of how the development of our app is progressing. We've gone a step further though in our workspace and linked this to our product ideas, marketing plan and more.
This template is designed for the Scrum methodology but if you prefer to use Kanban then it can be easily adapted.
You can see a preview of this template here.