Yes, your question is certainly well-timed, and thank you for your season’s greetings, which I gladly return: Christos anesti !
The only place I know of where Schuon speaks of Christ’s descent into Hell is in the chapter “The Particular Nature and Universality of the Christian Religion”; this may be found, as you know, in The Transcendent Unity of Religions, and I have also included it in my anthology The Fullness of God: Frithjof Schuon on Christianity. He is speaking about “the identification of historical facts with principial truths” in Christianity, “and the inevitable confusions resulting therefrom.” He continues as follows:
“For example, when it is said that all human souls, from that of Adam to the departed souls of Christ’s own contemporaries, must await his descent into Hell in order to be delivered, such a statement confuses the historical with the cosmic Christ and represents an eternal function of the Word as a temporal fact for the simple reason that Jesus was a manifestation of this Word, which is another way of saying that in the world where this manifestation took place, Jesus was truly the unique incarnation of the Word” (pp. 8-9 of The Fullness of God).
As for Orthodoxy, its teaching on the subject is, as usual, less juridical and more mystical than that found in the West. The Orthodox certainly agree with the Catholics that Christ “harrowed hell”, but rather than thinking He descended to the dead in order to liberate a specific number of souls, namely, those of the “righteous”, Orthodoxy construes the “event” to be a conquering of Death as such; hence the Paschal troparion, sung every Easter: “Christ is risen from the dead, trampling down death by death, and upon those in the tombs bestowing life.”
The icon of this “event” is most interesting: Christ is pictured pulling Adam and Eve, and by implication all of humanity, out of Hades. The figure of Christ appears inside a mandorla (this is the blue, star-studded, almond-shaped outline around the figure of Christ you see here). In the symbolic “language” of Orthodox iconography, this signifies that what is therein pictured was not an event occurring in space and time and that it could not have been “seen” with the empirical eyes. The “universal” implications of this image are obvious.