I touched on the Kadesh Priesthood from Deuteronomy in this post. Granted, the Leviticus 18:21,22 verses don't state directly; "We are the Kadesh being talked about here and not homosexuals," but two points, if true, will leave the connection with the Kadesh to Leviticus without question.
1. That cult prostitution existed in Canaan at the time of the Israelites.
2. That the Canaanites frowned on homosexuality outside of a cult worship setting and that the prohibition in Leviticus 18:22 can't be anything but homosexuality in the context of only idolatry.
The first point is easily proven by the Bible Itself in 1 Kings 14:24 and 22:46:
"There were even male shrine prostitutes (qā·ḏêš) in the land... "
"He rid the land of the rest of the male shrine prostitutes (haq·qā·ḏêš)... "
This is also backed by the historical record.
The second point clinches it because Leviticus 18;3 states the Israelites were not to do the practices of the Canaanites:
"You must not do as they do in Egypt, where you used to live, and you must not do as they do in the land of Canaan, where I am bringing you. Do not follow their practices."
Now if it can be shown that the Canaanites did not have homosexuality outside of their cult ceremonies or even prohibited homosexuality outside those ceremonies, that means homosexuality was not one of the Canaanite "practices" God is forbidding and Leviticus 18:22 and 20:13 falls squarely into the 'cult male prostitution' category.
The Canaanite record is silent on homosexuality either way, but In his book "The Hebrew Bible: New Insights and Scholarship," Frederick Greenspahn states the Canaanite law codes where directly copied from Mesopotamian Law Codes and what do we find in MAL: 19, 20? A rumor of homosexuality being slanderous and a general prohibition of homosexuality outside pederasty and idolatry. We can now say homosexuality was not only not a "practice," but it was also prohibited by the Canaanites if they indeed copied Mesopotamian Law.
(note; there was no variance in views within the Mesopotamian Nations on homosexuality. What you read here is all there is.)
The Hittites would also have copied the Mesopotamian Law Codes on homosexuality because of era and being close neighbors to the Canaanites, but again, nothing is stated outright about homosexuality either way. What we do have though are several Hittite historical documents that hint at how homosexuality was held by this people. One is the "Siege of Ursu" text that had a Hittite army commander criticizing his men for acting as "kulessar," what historians believe is acting like a passive homosexual. The other is an exorcism text called the "Ritual of Anniwiyani" who's purpose was to exorcise an "effeminate" demon.*
As for Egypt? The land the Israelites left who's "practices" they were ALSO forbidden to follow by God? Even homosexual desire was condemned according to the "Egyptian Book of the Dead" and Derrick Sherwin Bailey states the ancient Egyptians regarded homosexual practices as; "... morally objectionable and personally degrading."
So there you have it. Homosexuality was rejected by the Egyptians whom the children of Israel left and from the evidence it was in all probability also forbidden by the Canaanites who's land the children of Israel were going to. This would make homosexuality not one of the practices God is forbidding in Leviticus 18 verse 3 with the two lands and that would make the homosexuality in verse 22 only in the context of idolatry, a necessary evil in their cult religion with the Kadesh.
This is an angle I don't think any researcher has gone into and it needs to be delved into with more depth.
*To the ancients, a male who was passive, willingly, was what they would have the closest definition of a "homosexual," at least in their minds. A male who was penetrative in a homosexual act, either to humiliate the defeated in battle or as a sexual outlet was never considered a male desiring other males.
How much the ancients knew about a 'gay sexual orientation' as we understand it today is for another discussion.