In chapter 3 of his De errore profanum, Firmicus Maternus apparently discusses Attis, although without naming him. Supposedly it says:
In the first half of the fourth century CE, Firmicus Maternus reports that “he whom they had buried a little while earlier [Attis] had come to life again.” (from here)
There seems to be no English translation online. I’ve made one here from the 1905 edition.
III. (1) The Phyrgians who live at Pessinus around the banks of the river Gallus, assign first place to the earth over the other elements, and this they profess (volunt) is the mother of all things. Then, so that they also might have for themselves an order of annual sacred events, they have consecrated the love affair of a rich women, their queen, who chose to punish tyrannically the scorn of an adolescent lover, with annual lamentations. And to satisfy the irate woman, or to find consolation for her remorse, he whom they had buried a little earlier, they claim that he had come back to life. And as the soul of the woman burned with the impatience of excessive love, they built temples to the dead youth. Then they profess that the priests appointed should undergo from themselves what the angry woman had done because of the injury to her scorned beauty. So in the annual sacred rites in honour of the earth the pomp of his funeral is organised, and when men are persuaded that they are honouring the earth, they are (in fact) venerating the death and funeral of a wretch.
(2) Here also, most sacred emperors, in order to shield this error, they profess that these natural sacred rites are also arranged rationally. They profess that the earth loves its fruits, they profess that Attis is exactly this, which is born from fruits; however the punishment which he sustained, this they profess is what the reaper with his scythe does to the ripe fruits. They call it his death when the collected seeds are stored; life again, when the sown seeds sprout in the turning of the years.
(3) I would like them now to reply to my inquiry, why have they associated this simple (story of) seed and fruit with a funeral, with death, with scorn, with punishment, with love? Was there not anything else that might be said? Was there not anything else that poor mortals might do in grateful thanks to the highest God for the crop? So that you can give thanks for the reborn crop, you howl; so that you rejoice, you weep. And you, when you see the true reason, you do not finally repent of doing this, but you do this, so that busyied with the turning seasons, you still flee from life, you pine for death.
(4) Let them tell me, how it benefits the crop, that they renew their tears with yearly howlings, that they groan over the calamities of a reborn corpse, which they say is arranged for a natural reason. You mourn and you wail, and you cover your mourning with another excuse. The farmer knew when he could furrow the earth with a plow, when he could sow the furrows with grain, he knew when to gather the crop ripened by the heat of the sun, he knew when to tread out the dried crop. This is the natural reason, these are the true sacrificial rites, which are carried out by the yearly labour in men of healthy minds. The divinity asks for this simplicity, that men should follow the laws ordained of the seasons (temporum) in collecting crops. Why do they try to explain this order by wretched fictions of a death? Why is that shielded with tears, which does not need to be shielded? From which let them admit of necessity, that these rites are not held in honour of the crops, but in honour of an unworthy death.
(5) When they say that the earth is the mother of all the gods, and they allot the chief roles to this element, indeed it is mother of their gods, — this we don’t deny or refuse, because from it they are always making their bunch of gods, whether of stone or wood. The sea flows around the whole earth, and again it is held tight by the circle of the encircling embracing Ocean. The heavens also are covered by the lofty dome, blown through by winds, splashed by rains, and in fear, as shown by tremors of unremitting motion. What remains to you, who cultivate these things, consider; when your gods reveal their weakness to you in daily declarations.
Here is the Latin, from the 1905 Teubner of Ziegler from Archive.org (tided up a bit):
III. Phryges qui Pessinunta incolunt circa Galli fluminis ripas, terrae ceterorum elementorum tribuunt principatum, et hanc volunt omnium esse matrem. Deinde ut et ipsi annuum sibi sacrorum ordinem facerent, mulieris divitis ac reginae suae amorem quae fastus amati adulescentis tyrannice voluit ulcisci, cum luctibus annuis consecrarunt, et ut satis iratae mulieri facerent, aut ut paenitenti solacium quaererent, quem paulo ante sepelierant revixisse iactarunt, et cum mulieris animus ex inpatientia nimii amoris arderet, mortuo adulescenti templa fecerunt. Tunc quod irata mulier pro iniuria spretae fecerat formae, hoc ordinatos a se pati volunt sacerdotes. Sic annuis sacris cum honore terrae istius funeris pompa conponitur, ut cum persuaderetur hominibus quod colant terram, miseri funeris venerentur exitium. Hic quoque sacratissimi imperatores ut error iste celetur, etiam haec sacra physica volunt esse ratione conposita. Amare terram volunt fruges, Attin vero hoc ipsum volunt esse, quod ex frugibus nascitur, poenam autem quam sustinuit hoc volunt esse, quod falce messor maturis frugibus facit. Mortem ipsius dicunt, quod semina collecta conduntur, vitam rursus quod iacta semina annuis vicibus reconduntur. Vellem nunc mihi inquirenti respondeant, cur hanc simplicitatem seminum ac frugum, cum funere, cum morte, cum fastu, cum poena, cum amore iuncxerunt? Itane non erat aliud quod diceretur? Itane non erat quod in agendis deo summo pro frugibus gratiis faceret misera mortalitas? Ut gratias pro renatis frugibus agas ululas, ut gaudeas plangis, nec te cum veram rationem videris, hoc aliquando fecisse paenituit, sed hoc agis ut annuis luctibus occupatas vitam semper fugias mortem requiras. Dicant mihi quid hoc frugibus profuit, ut fletus suos annuis ululatibus renovent, ut renati funeris calamitatibus ingemescant, quod dicant physica ratione conpositum? Lugetis et plangitis, et luctus vestros alia ratione celatis. Novit agricola quando terram aratro dimoveat, novit quando sulcis frumenta committat, novit quando maturatas solis ardoribus colligat segetes, novit quando tostas terat fruges. Haec est physica ratio, haec sunt vera sacrificia, quae ab sanae meniis hominibus annuo labore conplentur, hanc simplicitatem divinitas quaerit, ut homines in colligendis fructibus ordinatis temporum legibus serviant. Cur huic ordini miserae mortis figmenta quaesita sunt? Cur celatur lacrimis quod celari non debuit? Unde confiteantur necesse est, haec sacra non in honorem frugum sed in honorem esse conposita mortis alienae. Nam quod terram matrem esse omnium deorum dicunt qui huic elemento primas tribuunt partes, vere deorum suorum mater est, nec abnuimus aut recusamus, quia ab hac collectos deos suos aut lapideos faciunt semper aut ligneos. Terram omnem circumfluunt maria, et rursus inclusa Oceani ambientis circulo stringitur, caeli etiam rotunda sublimitate operitur, perflatur ventis aspergitur pluviis, et timorem suum assidui motus tremoribus confitetur. Quid vos maneat qui haec colitis considerate, cum dii vestri infirmitatem suam vobis cottidianis confessionibus prodant.
I always sigh on seeing so large a chunk of Latin.
This is a very different earth cult to the one represented in the other sources.