Here is the requirement to be Indigeneous. The third point says ,Not Included in Hindu cast system I guess newars are Hindus.

http://www.nefin.org.np/list/Definition-of-Indigenous/5/0/4

• First settlers  prior to the formation of Gorkha and Nepal state. 
• Dominated group and no representation in state organs 
• Not included in the Hindu cast system.
• Own language, culture and religion different from the rulers.
• Listed by Nepalese Government Indigenous Act 2002.

• Fall under Hindu cast system.
• 86% representation in the civil service.
• Not listed as IP’s by Nepalese Government Indigenous Act 2002.
• Not recognized as IP’s in India  and migrated from India to Nepal.
   

kash such as Basnyats , Bistas, karkis, khadgas were converted to chhetries. they migrated in Nepal before the chettery bhaun invasion from india later converted to chhetries because they were brainwashed by the bahuns that being khas and to live without wearing janai is one of the lowest status in the caste system. Now khas are almost extinct. they used to worship their own gods as kuldevtas who were not hindu gods. this is my understanding of khas. please correct me if i am wrong. Now the chhetries don't even like to call them khas and only worship their kuldevatas once in a while and mostly worship hindu gods as shown in indian channel.. so if there is any indigenous race in Nepal that is Khas.

Most of these ppl must be good in history.