So reading Catechetical Letter 3 St Cyril states

4. For since man is of twofold nature, soul and body, the purification also is twofold, the one incorporeal for the incorporeal part, and the other bodily for the body: the water cleanses the body, and the Spirit seals the soul; that we may draw near unto God, having our heart sprinkled by the Spirit, and our body washed with pure water. Hebrews 10:22 When going down, therefore, into the water, think not of the bare element, but look for salvation by the power of the Holy Ghost: for without both you can not possibly be made perfect. It is not I that say this, but the Lord Jesus Christ, who has the power in this matter: for He says, Unless a man be born anew (and He adds the words) of water and of the Spirit, he cannot enter into the kingdom of God. John 3:3 Neither does he that is baptized with water, but not found worthy of the Spirit, receive the grace in perfection; nor if a man be virtuous in his deeds, but receive not the seal by water, shall he enter into the kingdom of heaven. A bold saying, but not mine, for it is Jesus who has declared it: and here is the proof of the statement from Holy Scripture. Cornelius was a just man, who was honoured with a vision of Angels, and had set up his prayers and almsdeeds as a good memorial before God in heaven. Peter came, and the Spirit was poured out upon them that believed, and they spoke with other tongues, and prophesied: and after the grace of the Spirit the Scripture says that Peter commanded them to be baptized in the name of Jesus Christ Acts 10:48; in order that, the soul having been born again by faith , the body also might by the water partake of the grace.

He later teaches Baptism of blood

10. If any man receive not Baptism, he has not salvation; except only Martyrs, who even without the water receive the kingdom. For when the Saviour, in redeeming the world by His Cross, was pierced in the side, He shed forth blood and water; that men, living in times of peace, might be baptized in water, and, in times of persecution, in their own blood. For martyrdom also the Saviour is wont to call a baptism, saying, Can you drink the cup which I drink, and be baptized with the baptism that I am baptized with Mark 10:38? And the Martyrs confess, by being made a spectacle unto the world, and to Angels, and to men 1 Corinthians 4:9; and you will soon confess:— but it is not yet the time for you to hear of this.

Since Trent does not mention Baptism of blood anywhere, I take this to be an error.

However the point of this thread is to discuss if St. Cyril teaches Baptism of desire anywhere. Since as seen above, he holds that water baptism is necessary for salvation (and makes an exception for BoB).

Despite claims to the contrary, St. Ambrose did not teach BoD.  St. Augustine taught it during his youth but later emphatically rejected it.  Those two there, "Augustine and Ambrose", have wrongly been used in all subsequent theorizing about BoD as the "authority" for BoD.

This is where St. Ambrose's oration of Valentinian has been completely misunderstood.  He believed that Valentinian, like the martyrs, could obtain some of the grace of Baptism, the washing part, but said in the same speech that "not even the martyrs are sealed", even though they are "washed".  But the seal was considered essential by the Church Fathers for entry into the Kingdom.

So later, Pope Innocent II opines in favor of BoD "on the authority of Augustine and Ambrose", and St. Bernard said that he'd rather be wrong with Augustine than right on his own.  These two opinions actually turned the tide of the debate in favor of BoD, but they were both mistaken.  Not only is it absurd to ignore the 5-6 Fathers who rejected BoD (what were they, chopped liver? ... did Augustine and Ambrose have some kind of higher authority than these others?), but both Innocent and St. Bernard were simply WRONG that these two taught BoD.  St. Augustined did ... for a while ... but then later rejected it.  St. Ambrose never taught BoD.

Interestingly, even Catholicism.org couldn't understand St. Ambrose, chalked it up to either a contradiction or to some unknown factor.  Well, the answer is right there in the text where St. Ambrose says that not even martyrs are sealed.

If you take St. Augustine and St. Ambrose out of the mix, then you end up with ZERO Patristic support for BoD.  So, not only do you not have unanimous Patristic consensus in its favor, but you have NEAR-unanimous Patristic REJECTION of BoD, and it's 100% unanimous of you take the opinion of St. Augustine later in his life rather than his former opinion.

If you take St. Augustine and St. Ambrose out of the mix, then you end up with ZERO Patristic support for BoD.  So, not only do you not have unanimous Patristic consensus in its favor, but you have NEAR-unanimous Patristic REJECTION of BoD, and it's 100% unanimous of you take the opinion of St. Augustine later in his life rather than his former opinion.

Early this year I was reading Faith of the early fathers volume 1, and I saw one of the fathers mentioning either BoD or BoB. But I can't remember which one...and I really don't want to read through 200+ pages to see whether it was BoD or BoB....

I can see from the downvotes on the OP that some people are very sensitive.. which is kinda sad. Unless someone can find a quote showing St Cyril teaching BoD that's another father who rejected it. And even if a quote is found, it would only be a contradiction showing that even the fathers can err.