Complex sentence: They find that in particular, the evidence for the subclassification or even ST affiliation at all of several minor languages of northeastern India is either poor or absent altogether, and that many such languages would for now be best considered "internal isolates" within the family.
Split into simpler sentences: They find that the evidence for the subclassification or even ST affiliation at all of several minor languages of northeastern India, in particular, is either poor or absent altogether. In their view, many such languages would for now be best considered unclassified, or "internal isolates" within the family.