They weren't. They were overwhelming Scandinavian and Northern European.
The one non-European was a Lapplander.
This is like "1 of 4 homeless are women" executive summary.
Also, going back to 2400 BC is going back thousands of years before the peak of the Viking Era (800-1200). Going forward to 1600 is silly. The Vikings weren't raiding England and Netherlands in 1400AD.
So, are these other studies suggesting diversity a version of faked academia attempting to break the 'monolithic race' message, or at worst purposely misleading commentary and editorializing on the data?
I wouldn't be surprised since the reputation of 'academia' is in the shitter.
The non-Scandinavian, non-European DNA? A single example of a Saami/Lapplander.