It can't be that hard to just dump/export the entire JIRA in one day and migrate it to something else like linear.app? i was already exporting HTML dumps of the entire JIRA and using it in local tool calls to ground agents as far back as last year instead of wrestling with JIRA API to get it to work. This was before linear became popular.

The migration would take 1-2 engineering man-days I suppose. But its money well spent.