Is there a supported method or even a how-to regarding the migration of bugs from Gnats to Jira?
I am not sure how you can export data from Gnats (haven't ever used it) but once you have it in a CSV or something, you can use the Importer in JIRA to import those issues.
There might be other options like using the JIRA remote API to create those issues but it depends on what Gnats can do.
It looks like you're new here. Sign in or register to get started.