It has to be one of two things.
1) There is a conspiracy amongst all print and TV news outlets, including GB News, the Daily Mail and the Telegraph not to print anything which could hurt the Labour Party
2) It isn't true
Regarding 1) I did some more digging and GB news have highlighted it via a video. Cant yet see it on any other sites.
Another possibility is that Media companies don't want to expose something that could lead to an investigation into their own billionaire owner(s) offshore tax affairs and highlight their hypocrisy.
Also possible some are waiting to verify it (although its now been 5 days so seems unlikely)
Michael Crick (ex BBC) has highlighted it.