Issue with dns on xbox, X and faceook

Hi, since installation i have had issue with virgin broadband through the hub 5. All was fine with BT. Xbox series x wouldn't connect to wifi and i had to set dns to 8.8.8.8, the xbox wont connect via ethernet though. Android phones wont work on x or facebook unless vpn is turned on and and laptops have an issue with MS teams. Hub has been factory reset by 2 engineers and a replacement hub was provided with the engineer having no clue. I figured out the dns issue and im thick. Any idea how this can be resolved?