Did you find the WAN side of your router, and confirm the ip address is 183.83.175.239
?
Are there any other boxes that are part of your home network?
To help visualize the network, I made a picture over on this thread-post
Here are general port forwarding instructions for Linksys routers. Looks similar to your screen shots above
I would also look at portforward.com and try to find your specific model. Sometimes steps can vary from model to model.
If you followed the steps correctly, but still have no joy, there are two possibilities:
1 there is another networking box somewhere on your network that you haven’t thought of
2 you ISP blocks that specific port. Some testing
If your ISP blocks the port 55000, tell Roon ARC to use a different port in:
1 Roon ARC
2 port forwarding rule