What is qtn.fortilink?

I've seen that pop up in my logs before, mate.

It is a domain name. Your FortiGate firewall uses it. The firewall needs to talk to the FortiGuard cloud. This is for all the security stuff. Like for web filtering rules and antivirus updates.

So it’s not for managing your switches. It is for getting security updates from the internet. It’s normal traffic for a FortiGate. You don't need to worry or block it. It just means the firewall is doing its job properly. No worries.