About the Upasakasila Sutta and LGBT

What you quoted is from Upāsakāśīla-sūtra (優婆塞戒經). The Upāsakāśīla Sūtra is a Mahayana Sūtra, and only a Chinese translation version exists now. The Upāsakāśīla Sūtra is adapted from Siṅgālovāda sutta and includes some contents about bodhisattva śīla (菩薩戒).

As for the 3rd precepts and lgbt, you can see this article (https://info-buddhism.com/Buddhism-Sexuality-Cabezon.html). I will talk other things the article doesn't mention.

The Mahayana Buddhism is a mixed Buddhism movement from Mahāsāṃghika, Sarvastivada, Vibhajyavāda (Theravada Buddhism), and other Buddhism sects, practicing the ideals of bodhisattva.

So, the 3rd precepts (and other Buddhism contents likewise) in Mahayana Sūtra would include the contents from these sects. The sexual misconduct including the condition of time, place, organ, non-female, is from the Abhidharma of the Sarvastivada, like Dharmaskandha (法蘊論), Abhidharmakośakārikā (俱舍論), Nyāyānusāriṇī (順正理論), etc.

The 3rd precepts in the "Pali Sutta" and the "Āgama Sūtra" of the Chinese version don't include the conditions in the Sarvastivada Abhidharma.

The quote appears to be from a Mahayana (Chinese) Sutra:

Sūtra of the Upāsaka Precepts
Translated from Sanskrit into Chinese in the Northern Liang Dynasty
by
The Tripiṭaka Master Dharmakṣema from India
Fascicle 6 (of 7)
http://www.sutrasmantras.info/sutra33f.html

But I don't know what that was translated from.

There's apparently also a Uposatha Sutta in Pali which is much shorter and doesn't have the (controversial) phrase in question. But I don't know where that sutta belongs in the Tipitaka.

See also What is the attitude toward h*m*sexuality in Buddhism?

No, that is not in Theravada Buddhism.

The 3rd precept deny only for breaking an agreement between people. In commentary allows even if the people can do an agreement together.

For the example, in the past people agreed with "marrying with 12 years old girl" because they thought parents or men are her owner and her protector form crime. The commentary allows follow to that agreement. However, it doesn't allow nowadays by same context in commentary because commentary also commented "Having sex with protected girl by law is breaking the 3rd precept, too".

As far as i can tell that text is not considered canonical by Vibbhajavadin schools, schools of analysis, monks who rejected some inessential parts of mainstream doctrine as it was then taught on account of it not being canonical, from which Theravada developed ca 250 BC.

I think text belongs to schools that were considered heretical by Theravada and would be among Mahayana texts.

Early texts offer little commentary but there is some.

There is a story in Theravadin Vinaya of a "pandaka" monk who first asked elder monks to attack him, then asked younger monks inb4 asking novices to attack him [a term used for sexual things, masturbation is called 'attacking with hand'] and being refused he wen't on to have sex with lay stable handlers and bad report spread about monks among lay people as a result.

A rule was made prohibiting pandaka ordination but the definition of a pandaka isn't clear, is very vague and describes some behaviors that have to do with being gratified only by ingesting s*m*n and or other particular deviances based on phases of the moon and whatnot, there is really no word for what is said to be pandaka in Theravadin Vinaya.

Same-sex sexual intercourse is not a cause for disrobing for a nun but is a disrobing offense for a monk. There are some differences here.

There are also mentions of a monk's peculiar fascination with the Buddha, he had to be sent away to train in solitude because he was so fond of seeing Buddha's form that it interferred with his training; but he was never referred to as to any terminology akin to gay, pandaka or anything close and whether it would be considered gay at this point is a moot point. He was one of the chief disciples, foremost in faith.

It is important to note that in the beginning gay people were certainly allowed to become monks as there were little to no rules. It is also unclear whether they were allowed to ordain throughout Buddha's life but nobody was forced to disrobe because of new rules afaik.

It is also clear that they were extremely tolerant in not beating up that monk who went around soliciting novices... Iirc when he asked monks told him 'go away pandaka, what good is that..'

If anything i think pandaka is closer to sexually perverted degenerate or a maniac maybe more so than a particular orientation. It's my opinion tho.

There is also a story about a group of monks who were aroused by seeing corpses in course of their training when visiting a charnel ground.

There is more to further analysis but i will leave it here. I think that if one puts it all together it paints a fairly tolerant culture.

Unfortunately traditionally Buddhist cultures do not generally share these views, try asking a Sri Lankan if a Sotapanna can have sex and they will say yes but if you ask for specifics of what sex they can do, they will probably never talk to you again because of the cognitive dissonance they will there experience.