Not exactly answering your question (I know nothing about Kazakstan in particular), but AES the podcast had an episode on the aboriginal people of the USSR, where they interviewed two canadian scholars who wrote a book "When the North Was Red: Aboriginal Education in Soviet Siberia". It was in two parts, part 1 and part 2. This can offer an interesting perspective on the rights of indigenous peoples and maybe some glimpse on treatment of minorities in the USSR.