IIRC, originally the camps were set up to house “Enemies of the state” and previous to the invasions of other countries this included: communists, socialists, roma, jehovah’s witnesses, homosexuals, and persons convicted of socially deviant behavior in 1933.
With the invasion of Austria in the spring 1938 the first mass incarceration of Jews happened and later that fall after “riots” like the “Night of Broken Glass” were spurred on by events like the assassination of Ernst vom Rath in Paris.
This resulted in mass arrests of adult male Jews where they were held in camps for brief periods.
When they invaded Poland in September 1939 the policies started to escalate, and the efforts that lead to the mass incarceration and eventual genocide started.
The Nazi party had started discrimination in 1933, and there was anti-Jewish legislation, economic boycotts etc… but it was in the summer of 1941 when Hermann Goering authorized action for a “complete solution of the Jewish question.”
It may be useful to remember that in 1934 they established the “Information Centers for Genetic and Racial Hygiene” based on the beliefs of eugenics.
Unlike the Socialists or other groups like the Witnesses that refused to sign allegiance the Jewish population was considered a poisonous “race”. While the slaves were also considered inferior and thus open to subjugation they view the Jewish population as racial enemies.
Remember that in 1939 30% of Warsaw’s population was Jewish and the European portion of Russia was also one of the largest Jewish populations in Europe.
While there are complexities around the dual cultural and religious implications of the Jewish religion the primary motivators were a falsified scientific belief in race, and the Nazi party was willing to use them as forced labor or subject them to inhuman medical experiments until the population reached a critical point where they escalated to genocide.
While the social realities of the false construct of “race” still are with us, the mainstream eugenics ideals have waned in popularity. But from the Nazi mindset it would have been primarily been a racist mindset that drove their actions. But non-ethnic converts would have been either considered enemies of the state or perhaps considered just inferior enough for subjugation.
To be clear, there is no scientifically sound basis for the concept of “race” and it is purely a sociological construct. As it is based on arbitrary criteria the edge cases will very depending on the differences of opinion of the individuals who were in power.
I will ask for clarification from other posters, but I can only find the Jewish and Roma populations as being officially designated as “enemies of the race-based state”. But I thought there were more so if you can correct my error or confirm this I would appreciate it.
Edited to add, Afro-Germans were also officially declared “enemies of the race-based state”