These are exactly the right screenshots. Seems straightforward enough in the screenshots. First, make sure to disable UPnP in the first screenshot. Then set up a manual rule in the page from your second screenshot as follows:
- Rule name: Roon (this is just a name)
- Select device: probably you can pick your Mac mini by name from a list
- External and internal ports: Look up the port number Roon is using, in the Roon ARC settings in the remote. Then enter it 4 times here in the 4 fields. (There are 2 fields each for external and internal because it would be possible to enter a range of ports, but Roon uses only one, so enter the same number)
- Protocol (half cut off in the screenshot): you can probably choose TCP or UDP here, pick TCP
Like this in the SH thread (use the port numbers your ARC settings tell you in the remote):
(Leave the IPv6 off)
Let’s see how this goes