By default, Traefik picks up exposed ports for every app using the default dockerfile. If for some reason the developer did not add this port to the dockerfile or multiple ports are exposed, we may have to tell Traefik which port to use for the web UI.
For Unraid, find the app that you would like to reverse proxy, once you are in the template, scroll to the bottom and click on the "Add another Path, Port, Variable, Label or Device". Select to add a label and fill in the fields as per the screenshot below.
Make sure to set this as a Label.
Copy and paste the following into the key: field, make sure to swap out app for the app name you are adding this to.
Tell Traefik which port to use for this app, simply add the UI port to this field.
Click add and then apply to redeploy the app with the new label added to it.
WARNING
You must replace app with the name of your application that this label is being added to otherwise Traefik will see duplicates.
PLEASE NOTE
You can add multiple of these labels at once before finally deploying your application.
Traefik will now use the port specified to forward all traffic onto the app correctly. Now when you deploy your application, you will be able to visit it by going to your domain with the app name as the subdomain (APP-NAME.DOMAIN.COM).