This article, if correct, suggests that the 'new' channel E4 Extra will be on Virgin Media 337, in the music section...
https://rxtvinfo.com/2022/first-look...ras-launch-day
It's actually a rebrand of the current 4Music, with a new version of 4Music launching on Virgin Media 336, which is itself a rebrand of Box Hits.
Come on VM, use some common sense and put E4 Extra in the Entertainment section like it will be on Sky.