As vintermann said - there's no evidence for any group arriving earlier than any others. We know that the "Norwegian" population in modern Norway are a mix of the original European population and the Yamnaya and others, we don't know exactly when that population overtook the earlier one (what's certain is that people who lived along certain parts of the coast 11k-12k years ago didn't have any Yamnaya connection, obviously). We don't really know much, except that the Sami languages haven't diverged enough from related languages elsewhere for them to have been there that long ago. The Sami came much later than the post-glacial original population. When the ancestors of modern Norwegian and Sami groups (and others) arrived we simply don't know for certain. If you look at the very oldest writings you'll find that there were a great many different groups of people in Norway, including in the far north-east, and there was trade. That lasted all the way up to the arrival of Christianity, after that this (if related, or just a coincidence) became more of a "take, don't trade" business.

Maybe opening a can of worms here, but no... actually they/we didn't.

19th century scholars were happy to declare that the Sami were the original inhabitants of the north, but that had more with the fact that they preferred seeing themselves as the superior, colonizing culture, than with archeological and linguistic evidence. Being a native was not cool at all. It was awkward for these scholars to become gradually aware of Sami's relationship to Hungarian and languages from further east, and even more such things as the -anger names core Sami areas Porsanger, Varanger, Malangen etc.

Angr is a proto-Nordic word that means bay. -Angr names are common all over Norway. We know that the word went out of use before 800 though, because around that time Icleand got settled, and there are no -angr names in Iceland.

There are even proto-Norse words preserved in Sami place names such as Máhkarávju - Avju is a proto-Nordic/proto-Germanic word for island. Máhkarávju is quite clearly related to the modern Norwegian name for the island, Magerøya, but that means they must have borrowed the name more than thousand years ago.

It may seem that the many proto-Norse borrowings in Sami may come from that in at least some parts of the country some of the time, it wasn't Norse culture and language that supplanted the Sami, but vice versa! Very awkward for scholars who would rather stake their nationalistic claims on manifest destiny than being first.

Now, Sami activists say any of this doesn't matter, because the Sami were a minority people with their own established culture and languages who were around when the formal borders of Norway were drawn up (as late as 1750 in Finnmark). And that's the ILO 169 definition.

This is completely true. It's also true that Sami activists were actively involved in writing that definition so that it would include them. I totally respect why they did that piece of lobbying work - the Sami certainly have legitimate interest to defend, and for that purpose being classed with native Americans is much more useful than to be seen as just another quarrelsome European linguistic minority like Welsh, Basque or Catalan people - or, say, people who use Nynorsk! (just see the hate they get in this very thread).