sure! so, the problem with classical historiography is an extreme paucity of sources. many, many contemporary histories of the early roman empire just don't exist anymore--we know about many of these, because they are referenced, cited, and quoted by works that we do have--but they just fell out of circulation in the 2000-odd years since they were written and there are simply no remaining copies.
this means that the later we go back, the more we have to rely on a smaller number of sources, which were also on average written later after the events they describe, which have also often only survived in abridged, incomplete, or translated form. obviously, there's no such thing as an 'unbiased' source, so the best way to get an accurate picture of historical events is to try and read as broadly as possible and make comparative assessments of different claims and the positions from which these claims are made -- this is really fucking difficult for a lot of Roman history, because often the number of sources describing a specific event will be in the low single digits.
we have three (!) substantive Roman histories of the reign of elagabalus: the contemporary cassius dio and herodians' accounts and the sensationalist and mostly-fabricated 4th-century historia augusta. now, all three of these describe him as effeminate, certainly: but these are claims that need to be contextualised. when elagabalus ascended to power, he was the high priest of a syrian cult worshipping the solar diety of the same name. the stereotype of the effeminate, barbaric foreigner from the east was a very prevalent one in the ruling class discourses of the roman empire: herodian is very clear that elagablus' effeminacy is inextricably tied to his easterness:
Leaving Syria, Elagabalus proceeded to Nicomedia, where he was forced by the season of the year to spend the winter. Immediately he plunged into his mad activities, performing for his native god the fantastic rites in which he had been trained from childhood. He wore the richest clothing, draping himself in purple robes embroidered in gold; to his necklaces and bracelets he added a crown, a tiara glittering with gold and jewels. His dress showed the influence of the sacred robe of the Phoenicians and the luxurious garb of the Medes. He loathed Greek and Roman garments because they were made of wool, in his opinion an inferior material; only the Syrian cloth met with his approval. Accompanied by flutes and drums, he went about performing, as it appeared, orgiastic service to his god.
When she saw what Elagabalus was doing, Maesa was greatly disturbed and tried again and again to persuade the youth to wear Roman dress when he entered the city to visit the senate. She was afraid that his appearance, obviously foreign and wholly barbaric, would offend those who saw him; they were not used to such garb and considered his ornaments suitable only for women
— Herodian, Book VI (emphasis mine)
the clarity with which Herodian makes this link is very helpful in considering how we conceptualize the accusations -- and they are accusations, they are intended to be read in a profoundly negative light by their audiences as signs of foreign decadence and perversion -- made by Cassius Dio. it gives us some hint of the constellation of tropes which the Romans had around foreign gods, foreigners (and Easterners specifically), and effeminacy.
Cassius Dio himself was also very much favoured in the government of Elagabalus' successor, Severus Alexander, who came to power after Elagabalus, his mother, and several influential figures in his court were assassinated by the imperial bodyguard. understanding these tropes and Cassius' natural inclination to flatter Elagabalus' successor, the reigning emperor and therefore his patron, we might therefore rightly treat Cassius' extravagant accounts of Elagabalus' behaviour, with great skepticism!
so, like, what was elagabalus' deal, then? we just don't know, because these three sources, all bound up in the Roman cultural image of degenerate Eastern effeminacy, one of them comically unreliable and noncontemporary, are all we have! there is of course, some archeological evidence: coins bearing inscriptions of the meteorite which Elagabalus' cult worshipped seem to confirm parts of the narrative wrt Elagabalus trying to introduce the primacy of his own god into Roman publc life: but there are no accounts from sources who were close to or knew Elagabalus, let alone anything from Elagabalus himself!
so, like, was Elagabalus 'transgender'? (leaving aside the question of applying modern frames of queer sexuality/presentation/etc to ancient subjectivities, which is a different if slightly related can of worms). well, the quotation typically given by supporters of this reading is generally from Cassius Dio, attributed directly to Elagabalus:
"Call me not Lord, for I am a Lady."
wow, seems pretty open and shut, doesn't it? now let's put it in context:
Aurelius Zoticus, a native of Smyrna, whom they also called "Cook," after his father's trade, incurred the emperor's thorough love and thorough hatred, and for the latter reason his life was saved. This Aurelius not only had a body that was beautiful all over, seeing that he was an athlete, but in particular he greatly surpassed all others in the size of his private parts. This fact was reported to the emperor by those who were on the look-out for such things, and the man was suddenly whisked away from the games and brought to Rome, accompanied by an immense escort, larger than Abgarus had had in the reign of Severus or Tiridates in that of Nero. He was appointed cubicularius before he had even been seen by the emperor, was honoured by the name of the latter's grandfather, Avitus, was adorned with garlands as at a festival, and entered the palace lighted by the glare of many torches.
Sardanapalus, on seeing him, sprang up with rhythmic movements, and then, when Aurelius addressed him with the usual salutation, "My Lord Emperor, Hail!" he bent his neck so as to assume a ravishing feminine pose, and turning his eyes upon him with a melting gaze, answered without any hesitation: "Call me not Lord, for I am a Lady." Then Sardanapalus immediately joined him in the bath, and finding him when stripped to be equal to his reputation, burned with even greater lust, reclined on his breast, and took dinner, like some loved mistress, in his bosom. But Hierocles fearing that Zoticus would captivate the emperor more completely than he himself could, and that he might therefore suffer some terrible fate at his hands, as often happens in the case of rival lovers, caused the cup-bearers, who were well disposed toward him, to administer a drug that abated the other's manly prowess. And so Zoticus, after a whole night of embarrassment, being unable to secure an erection, was deprived of all the honours that he had received, and was driven out of the palace, out of Rome, and later out of the rest of Italy; and this saved his life.
okay, so: the context for this quotation, which Dio attributes to Elagabalus, is: he is saying this to an athlete, who he has had brought to him by the men he hires to find men with gigantic penises, before his other gay lover poisons the athelete with limp-dick pills and Elagabalus, enraged that the man cannot fuck his ass because of this, banishes him from Italy. we might, i think, fairly say, that this is far from a neutral recounting of the emperor's own words, and i think we may in fact go further and say that this seems very obviously an overwrought scandalous fabrication. but putting all that aside: how does Cassius Dio know the emperor said this? he does not seem to have been present at this event -- if he spoke to someone who was, or pulled from the written account of someone who was, or if he pulled this from someone who also wasn't there, or if it was revealed to him in a dream -- we don't know! we have no way of knowing if any of this happened, or what real events it might have been based on. we literally just don't know, and it's unlikely we'll ever know!
and, y'know, this is just one example. there are countless stories about roman emperors doing crazy sex acts and enacting ridiculous violence, and in many cases these are obviously written to flatter their succcessors who came to power when they were murdered -- and they're still all we have. so. it's kind of a bind. we know that the pictures of caligula, nero, commodus, elagabalus, and all the other 'bad emperors' are inaccurate, probably full of slander and exaggeration from their political enemies -- but we have very little else to go on to try and build a 'more accurate' picture of what they might actually have been like as individuals or as administrators. and
this is a problem that plagues not only these controversial individuals but entire societies, wars, epochs of history -- huge chunks of our modern understnading of Sparta comes from Plutarch, writing centuries after it stopped existing as an independent polity. other chunks come from Thucydides and Xenophon who, while more contemporaneous, were Athenians who never set foot in Sparta. and this is something i think that people who talk about ancient history in a like, casual sense really don't grasp, that it is genuinely just impossible to know for sure how much of what scant sources we have is true or not, except in the cases where things can be independently confirmed by archeological evidence. it's fascinating but daunting! and it's frustrating how often it's collapsed down into silly debates like 'was elagabalus trans' that can't possibly be answered in any meaningful way.