The same website the OP links to, which is an Australian site, has a page that includes the text, "Vitamin D deficiency may be a greater health concern for people with naturally very dark skin, as it is more difficult for people with this skin type to make vitamin D.".
It's unclear why an Australian site would be going into the question of who is "suited to" live in the UK.
I mean, the low case rates could be due to the lockdowns, not sure about mortality rates unless you're comparing it to places where the ICUs have become overwhelmed.
It's unclear why an Australian site would be going into the question of who is "suited to" live in the UK.