Edit: see this Cloudflare app, portzilla.
Browsers are hard-coded to use port 80 for http:// connections and port 443 for https:// connections. They also don’t check SRV records, they only query for A/AAAA.
In order to get port 8080 to work for your domain, you will either need to go directly to example.com:8080 or use a proxy like Workers to proxy to another port number.
Also see this: How do i forward to a ip with a port number? - #5 by shimi