Hi I do not fully understand why you put it on IPV4 only there should be no need for that, I have a PS5 PRO and it runs on Sky broadband fine with no issues with zero changes made by me to router settings or PS5 network settings. I connect via Ethernet too.
Questions
1: Have you done a speed test on a device that is not the PS5 to make sure its not just the PS5 that has the issue?
2: Can you do a sky line test by logging into sky.com and going to support its not that hard to find and i am sure someone else on here can link to it.
If all fails contact sky but you really need to test with another device. Also if you can try the WIFI on the PS5 and see if that is any better encase there is an issue with your Ethernet cable/network.
