That's quite a black hole, knowledge-wise. Written accounts of any sort are really rare in that period and mentions of Sami are very sporadic. The Sami themselves have no written documents of that era, and their lifestyle makes it even more difficult to estimate how they may have been affected by the plague (e.g. no cemeteries). We don't really know if the Norwegians were disproportionately impacted compared to the Saami.

But we can say that the Sami underwent large social changes in the period, on the basis of archaeological evidence. Trade networks collapsed, including the Scandinavian-Sami trade in pelts. In the mid-1400s, metal objects would disappear from Sami sacrificial sites. The interpretation advanced by Inga Serning would be that this is because metal became too scarce for that, once they couldn't trade for it. An earlier alternate explanation from Hallström (in the essay Lapska offerplatser ) had was due to increased religious intolerance caused the Sami to move their sacrificial sites to secret locations. Serning argued that this seems very unlikely since it wasn't the case in the 17th century when the missionary activity was far greater, and really began in earnest. (which i why in a long post I wrote recently on Sami conversion, I started with the 17th century) No missionaries are even mentioned before 1419. This is also backed up by more recent radiocarbon dating showing that those sacrificial sites continued to be used - just without metal.

But it wasn't just the metal that disappeared, so did the stállotufter (plural, Swedish stallotomter ). These are oval rock circles with hearths in the middle belonging to Sami structures, which occur together in groups. (picture of an excavated one) They start appearing - and seem to have had their largest concentration - during the Viking Age. They then vanish in the mid 14th century, for about 300 years, after which they started being repurposed.

These are so common and yet so far removed in time that later Sami folklore would deem them to have been dwellings of the mythical Stallo, hence the name. Not much is certain about how these were used; whether they were used for hunting wild reindeer or early reindeer-herding. Nor whether the structure was a goahti and whether it was then a lávvu (the straight-pole, tipi-like tent) or a bealljegoahti (curved-pole structure).

Regarding the 'early' herding - Although many people today have the impression the Sami have been nomadic reindeer herders since time immemorial, this is in fact not the case. They're not recorded doing it until Olaus Magnus descriptions in the 16th century. (The Historia Norvegiæ from around 1200 describes them only as hunters and trappers) Even if reindeer pastoralism didn't gain full steam until later, it's possible that with certain groups it began as far back as the middle ages, and the Black Death may have been a triggering or at least contributing factor in the transition.

But ultimately there are no detailed written accounts of how the peoples interacted either before or immediately after. There are a few mentions of Birkarlar on the Swedish side but we don't really know what their job was at that time. There's a Norwegian ban on going to the Sami shamans to have witchcraft performed. Just little fragments like that.

In summary. Something happened. We don't know if the Sami were decimated by the plague or not. More recent evidence (see refs to Inga-Maria Mulk's work in the first book below) of the disappearing metal and habitation sites seems to indicate change rather than abandonment due to massive dying-off. But as said, the disruption of trade caused by the black death would explain the change in how metal was used.

Sources:

L.I. Hansen and Bjørnar Olsen, Hunters in Transition: An outline of early Sami history, 2014 (only a short summary of the Black Death bit but a good history in general)

Inga Serning, Lapska offerplatsfynd från järnålder och medeltid i de svenska lappmarkerna, 1956

Inger Zachrisson, The Saami metal deposits A.D. 1000–1350 in the light of the find from Mörtträsket, 1984