A look at what the historic record provides will help provide some context. There are a few notable descriptions (well, complaints) about Viking Age Scandinavian hairstyles influencing Anglo-Saxon style, probably the most famous being Abbot of Eynsham Ælfric's complaint to one "Brother Edward" about his wearing "the Danish custom" of his hair long in the front and short (shaven?) in the back. This description frequently raises comparisons to hairstyles worn by the (male) Normans in the Bayeux Tapestry.

Ælfric lived in the 10th and early 11th century. A much earlier (c. 793 CE) but notably vaguer description comes down to us from Alcuin of York complaining to Æthelred of Northumbria about Æthelred's 'pagan beard and haircut', but Alcuin provides no description beyond it being a matter of his concern. Descriptions of Viking Age Scandinavians don't often go into much detail and are in fact pretty rare, and few of them mention hair.

The archaeological record provides us with more insight, including into Viking Age female hair styles. A frequent motif found in the Viking Age archaeological record (and it would seem long before, with a very similar motif on the enigmatic Golden Horns of Gallehus from around the early 5th century CE), is that of a female figure bearing or holding something, often a horn or cup (like this one from Nygård: https://samlinger.natmus.dk/do/asset/2378 ). These depictions often feature a figure wearing a notable hair knot. Usually they're in profile, but a remarkable three-dimensional extension of this motif, in this case bearing a sword and shield, was found in Denmark a few years back: https://tinyurl.com/2tbuk5c2

I recall noting a lot of historic-inspired stuff in what I saw of the the show Vikings, but the show runners certainly did not restrict themselves to current understandings of the historic record. Such an approach isn't new for Viking Age Scandinavian-inspired material: The best known example is probably composer Richard Wagner's costuming decisions for his ring cycle, which generally have little to do with the historic record in favor of Wagner's creative vision, yet continues to influence modern ideas of the Viking Age.

You might also be interested in digging into the topic of earlier hairstyles among ancient Germanic language-speaking peoples. Consider the so-called Suebian knot, which seems to be mentioned as early as Tacitus's Germania (1 CE) and looks to appear several hundred years later on Migration Period bracteates (like this famous one: https://tinyurl.com/4bcmvytm ) This was an ornate braided hairstyle worn by males that disappears from the record (as far as I know, anyway) before the Viking Age.

Hair and beards also plays a central role in the origin story of the Lombards, and there's been a lot written about the importance of hair and beards among the Germanic peoples and other related peoples.

Finally, here's a list of relevant digital museum collections you might find handy for browsing items from the archaeological record:

https://www.mimisbrunnr.info/museum-resources-digital-collections

Edit: Shortened second and third URLs to solve for desktop versus mobile issues.

The "Viking" look - the long hair, usually braided on top, pulled tight at the sides - is really hard to find in artifacts or texts. From artifacts the style of hair for men seemed shorter - the beard seemed to be more important to the silhouette than the hair.

Tjängvide Stone - examples of Viking age portraits

The rider often associated with Odin / Sigurd has cropped, jaw-length hair. The woman greeting him, has a very tradition female hair style - a knotted ponytail. The same style is seen in a metal "Valkyrie" figurine from Hårby: Hårby figurine with women's hair knot:

There a cart found in the Oseberg ship burial with a number of "portraits" of real Norsemen (and women):

Man and Woman in profile relief carving

Carved 3-D man's face /figurehead on the body of the cart

From texts, hair is mentioned often, but there is an emphasis more on facial hair - and a certain standard having of men's facial hair versus any other single standardized hair style. In Njal's saga, there are beardless men who are held up as a negative example. So no beard = not cool.

The issue with finding examples of Viking hair styles is that the Norse tended to burn the dead - especially earlier on. Grave examples that survive tended to be high status burials or from a later period (influence of Christianity, likely). What is very interesting is that the hair was sometimes treated separately from the body - like that of grave from the Eastern Mound at Upsalla - it was cut off after death and buried alongside the grave occupant's ashes. There are a handful of these hair / ash burials.

There is a British text (supposedly by John of Wallingford) that describes how the Danes combed their hair everyday and bathed regularly. Combs are a common item found in graves, confirming this fixation on grooming. When you have names like Harald Finehair added to the equation, it seems plain that the Vikings were to some extent obsessed with hair and it's grooming. But that might be all you can say.

Fastidious attention to hair for their day - sure. The full, lucious beards - yes. The long hair with elaborate braids/plaiting - harder to prove. It was more likely short for men and in a simple ponytail/knot for women.