Planning tool for JIRA

[Jacob A. Albrektsen]

we are involved in product development, which currently not running in sprints or anything. i.e. that we develop and release with a release date that varies widely. We would like to perhaps switch to delivering in 2-3 week sprints, but would also like to have a better overview of the estimated time that will be used in a given sprint.

Therefore, I am looking for a tool (preferably free!) in Jira to manage my team members' time, to be able to plan and prioritize their time in terms of upcoming deliveries.

We are currently running Tempo app for JIRA but we don't have access to the Planner part and it doesn't seem like we can access it as it wasn't used when we had access to it.