Is there a consensus among the scholars that it is haram for a man to look at a non-Mahram (permanently unmarriageable) woman who wears the full hijab (including niqab), even if the look is not accompanied by desire? Or do scholars have different views regarding this issue? [Please do not refer me to questions that have already been asked on this website.]

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.

First of all, you should know that it is not easy to state decisively that there is a consensus on a certain issue. This is why Imaam Ahmad said, "Whoever claims an Ijmaa' (consensus) has lied; perhaps the people differed and he was not aware of it." However, this does not mean that there can never be a consensus; rather, it means that it is difficult to establish the existence of a consensus.

We could not find any scholar relating a consensus about what you mentioned in the question. Muslim scholars stated the permissibility of looking at the woman who wears her hijab without lust and the prohibition of gazing upon her with lust. The Hanafi book Fat-h Al-Qadeer reads, "It is allowed for the woman to see of a man what he is allowed to see of her, if there is no fear of Fitnah (temptation), because the ruling on looking at what is not ‘Awrah (parts of the body that must not be exposed) like clothes is the same for both men and women."

The Maaliki scholar Ad-Dusooqi wrote in his commentary, "It is prohibited to look at the uncovered ‘Awrah of another person even if it is without lust. But if the ‘Awrah is covered, it is permissible to look at it..."

The Maaliki scholar Ibn ‘Abd Al-Barr wrote, "As for looking with lust, it is prohibited to gaze at her body from over her clothes; not to mention looking at her unveiled face!" [At-Tamheed]

Allah knows best.