Because they were already there when Germany expanded into their territory and maintained a recognizable distinct identity.
Pretty much yes.
An argument can be made that the occupants of Livonia (now Latvia and Estonia) were indigenous people who ultimately managed to get their own nation-states. The northern crusades against the pagans began in the 12th century and the area was dominated by the Baltic Germans for centuries (under various supreme rulers including Sweden and the Czar)…and then later the USSR.
Throughout the 8+ centuries of occupation, they maintained their language (although lots of German/Russian words came in) and a lot of cultural traditions.
So Estonia and Latvia are good arguments for European indigenous people who actually managed to secure their status to the extent they have their own country. Not surprising, given their history, maintaining this independence is a big concern.
In addition, there are even smaller language sub-groups would include the Setos (15,000 people, Võros (70,000 people) and Livs (last native speaker died in 2013) around.
Baltic Germans - Baltic Germans - Wikipedia
Setos - Setos - Wikipedia
Võros - Võros - Wikipedia
Livs - Livonians - Wikipedia
I know nothing about the source but a cool map of minority languages/peoples in Europe
http://www.eurominority.eu/version/eng/minority-map.asp
First mistake I can see is they’ve have Northern Ireland weirdly delineated, including parts of the Republic, they also have statistics pertaining to the republic. It’s a bit of a mess to be honest.
The part of Sweden where Sami is spoken is very exaggerated and Finnish speakers in Sweden and Swedish speakers in Finland are absent.
Kinda-sorta - there were other Non-Inuit people before the Norse settlement, and there were Proto-Inuit after the settlement, with, as you note, some overlap. But the Thule were there before modern European continuity, so I’d still call them indigenous, just like I’d say the Guanches are indigenous Canary Islanders even though their occupancy only dates to ~1000 CE and it seems there were inhabitants before that.
Basque is shown as being spoken throughout all of Navarre, when actually in the Cuenca (Pamplona area), Ribera (center+south) and Sangüesa (Eastern) areas there are less speakers percent-wise than in some Montana counties. This is pretty much to be expected, though: we do have Basque as co-oficial in the region and don’t really expect outsiders to get into the subtlety of its actual geographic distribution (we’d be happy if they could just start getting the whole concept of “bilinguism”).
Also note that they seem to have missed the news that Valenciano is well on its way to separating from Catalan; food boxes printed in five languages (Spanish, Galego, Euskera, Catalan and Valenciano), Valencia’s government speaking of Valenciano, a very sudden linguistic change between Tarragona and Castellón where it used to be a smooth one, etc.
And Southern Italy is apparently linguistically and culturally homogenous with Northern Italy, which will come as a surprise to the Italians.
One interesting thing related to this is that a disproportionate number of Italian immigrants to the US were from Southern Italy due apparently to the worse economic situation there than in the north. The result of this is that “Italian-American” culture and cuisine is largely Southern Italian in origin. E.g. oregano, the so-called “pizza spice”, was historically unknown up north - it was something that Sicilians might use but certainly not up toward Switzerland.