Old Norse stories are not typically very detailed, and the amount of detail varies widely, but more often than not is is very short things like (in Saga of the Greelanders) "That winter Erik the Red died as well." (Þann vetr andaðist ok Eiríkr rauði.) or "Early that winter, disease came to Thorstein Eirikssons crew, and killed many of his travelling companions. (Þat var snemma vetrar, at sótt kom í lið Þorsteins Eirekssonar, ok andaðust þar margir förunautar hans.). So there's little way of knowing what kind of sótt (disease) they meant. Scurvy obviously presents itself as an option, and that was for instance suggested by explorer Fridtjof Nansen, who published his own analysis of the Sagas in In Northern Mists (1911).

When it comes to long-term mortality this was probably held down by milk, and scurvy-grass. To quote Nedkvitne, Norse Greenland 2019, p244:

According to the estimates above, milk provided ca. 53% of a Norse Greenland household’s calories, of which 47% came from cows and 6% from goats. Milk may also have protected the Norse Greenlanders’ health. In polar regions scurvy is a serious problem caused by a lack of vitamin C, which is mostly found in fruits and vegetables, among them cochlearia which grows in Greenland. But fresh milk also contains vitamin C, and for children this may have been particularly important.

The Sagas also write about bringing livestock with them on journeys as a common thing, so it probably was. Further, there was also a tradition of eating Scurvy Grass in northern Norway, and which we know was used in re-colonized Greenland, and not entirely unimportant in the history of scurvy (Nedkvitne, p300):

Cochlearia or “scurvy grass” was traditionally eaten along the coast of northern Norway and by Greenland Inuit as a remedy against scurvy. In his diary from 1728 Hans Egede wrote that in February-March many members of the Danish colony at Nuuk used to become sick with scurvy, but they were cured by eating cochlearia (Cochleare-Græs) which they found under the snow.

That finding was repeated by Johann Bachstrom, in his 1734 book Observationes circa scorbutum ("Observations on Scurvy") and Bachstrom was then cited by James Lind, famous for who was into researching the scurvy problem and suggesting citrus fruits, also wrote about the Greenland scurvy-grass in his book A Treatise on the Scurvy.

Which isn't to say it didn't happen people got it. The condition was known to the Norse; in the Saga of Thorstein the White (Þorsteins Saga Hvíta), composed in the 1200s but supposedly depicting earlier events, it's a plot point. Thorstein contracts scurvy (skyrbjúg) and was mocked and left to die but recuperates by unspecified means and comes back for revenge. In the Bishop's Sagas, Bishop Árni [Þorláksson] runs low on supplies and 'incurred a great scurvy in the mouth'. (fékk mikinn skyrbjúg í munninn).

At least from the few sources we have, it seems presented as dangerous and potentially lethal, but also recoverable. Which of course it is. It's also presented as associated with starving, in Árni's case, so there was perhaps a vague awareness of it being a deficiency of some sort.

The English term 'scurvy' may in fact derive from Old Norse skyrbjúg, which may be from skyr (as in Scandinavian soured milk, AKA tettemelk, taette, långfil) and bjúgr (swelling), hence a swelling caused by drinking skyr on long voyages perhaps. From whence it was loaned into Middle Low German as "schorbuk" and variants, and from there to English. Although an alternate theory is it that it originated in Low German with schoren (cut) and buk (abdomen), so belly-cut (or 'abdominal laceration'), and was loaned from that into Medieval Scandinavian. It doesn't occur in Norse sources old enough to determine.

A text from in a manuscript from the late 1400s, Lǽknisfrǿði, suggests a drink made out of the root of the Northern Dock (Rumex longifolius, modern Norwegian Høymole) - rotina af heimno. Which is interesting since it's not scurvy-grass, but could likely work as well.