(=Response to a discussion about the Bible not originally condemning homosexuality. The discussion is fairly lengthy=)

Your first two sentences are incorrect. Homosexual activity was proscribed from earliest Old Testament times as shown in Deuteronomy 23:17 & 18, 1 Kings 14:24 and 2 Kings 23:7.

The sin of Sodom that led to its demise was recognised in the Letter of Jude written probably cAD65 or possibly cAD80.

Errors, alterations and additions in and to biblical texts are well known to modern biblical scholarship, and a good study Bible illustrates these matters so that, I and all of today's readers are able to discern the original intent.

Concerning Leviticus 20:13. Your information, though informative, is not persuasive. To ritually defile someone (especially by accident) would have been seen as a hateful thing but not warranting the death penalty which we can see was ordered for the most serious of sexual offences.
Concerning your comment about Leviticus 18. Between vv6 - 23 there are 17 prohibitive verses regarding unlawful sexual relations and just 1 non-sexual prohibition. So, yes, this seems to be, with one exception, "all about sex".