The Urantia Book does not make any statements regarding either homosexuality or the gay lifestyle. There is a passage that extols friendship between persons of the same sex, but there is never any instruction regarding homosexual sex. There are, however, plenty of teachings concerning sex itself, and you can read our topical study on that subject HERE.
Many of the teachings about sex that you'll read in this study are presented in an historical context, i.e., how sex influenced primitive man, furthering the evolution of marriage and the resulting society. It is important to note that marriage between a man and a woman, resulting in children and family, is held by the revelators as the highest calling in life...so important that three entire papers are devoted to its evolution, its importance as a social institution, and its most important role in family life. You can read those papers starting HERE
Many of the teachings regarding sex have to do with pair-mating and marriage, but there is nowhere in The Urantia Book that either forbids or promotes same-sex attraction. This subject more properly falls under the category of the social mores, and in today's social culture, homosexuality and gay lifestyles are more socially acceptable that they ever have been. This issue is one that must be thought out prayerfully and thoughtfully by those who find themselves in that position. In the end, mutual love, respect, and devotion are always the guiding principles that should drive any relationship between two persons.
Thanks again for your questions. I hope my reply is helpful to you.