I recently had a call with a team I was assisting with something Jira-related, and they told me of an upgrade issue they were facing. They have valid Jira Server licenses and tried to upgrade to the latest LTS. After they upgraded were told their license was incompatible with that version of Jira. They had a valid license, and I have found no documentation stating that there is a version cap for Server products. Does this sound right?
I don't have access to this particular system, so I can't see it for myself.