I see. So you have no documentation that they knew Matthew was first. You will just state that they knew it.
Perhaps I posited on the other thread we are on. Doctor of the Church, bishop and historian St Augustine addressed Matthew as the first Gospel.
Augustine Harmony of the Gospels:
Chapter 2. On the Order of the Evangelists, and the Principles on Which They Wrote.
3. Now, those four
evangelists whose names have gained the most remarkable circulation over the whole world, and whose number has been fixed as four — it may be for the simple reason that there are four divisions of that world through the universal length of which they, by their number as by a kind of mystical sign, indicated the advancing extension of the
Church of
Christ — are
believed to have written in the order which follows: first Matthew, then Mark, thirdly Luke, lastly John. Hence, too, [it would appear that] these had one order determined among them with regard to the matters of their personal
knowledge and their preaching [of the gospel], but a different order in reference to the task of giving the written narrative. As far, indeed, as concerns the acquisition of their own
knowledge and the charge of preaching, those unquestionably came first in order who were actually followers of the Lord when He was present in the flesh, and who heard Him speak and saw Him act;
[...]
4. Of these four, it is
true, only Matthew is reckoned to have written in the Hebrew language; the others in Greek. And however they may appear to have kept each of them a certain order of narration proper to himself, this certainly is not to be taken as if each individual writer chose to write in
ignorance of what his predecessor had done, or left out as matters about which there was no information things which another nevertheless is discovered to have recorded. But the fact is, that just as they received each of them the gift of inspiration, they abstained from adding to their several labours any superfluous conjoint compositions.
CHURCH FATHERS: Harmony of the Gospels, Book I, Chapter 2 (Augustine)
St Jerome schloar, doctor and translator of the Latin Vulgate Bible.
“Jerome Preface to the Four Gospels - original Latin Text with English translation”
I am now speaking of the New Testament. This was undoubtedly composed in Greek, with the exception of the work of Matthew the Apostle, who was the first to commit to writing the Gospel of Christ, and who published his work in Judæa in Hebrew characters.
Jerome Preface to the Four Gospels
Church Historian Eusebius speaking of the works of Papias (early 2nd century AD):
On the Composition of Mark and Matthew, citing Papias [Bishop of Hierapolis in Asia Minor; lived ca. 60-130 AD]:
Papias gives also in his own work other accounts of the words of the Lord on the authority of
Aristion who was mentioned above, and traditions as handed down by the
presbyter John; to which we refer those who are fond of learning. But now we must add to the words of his which we have already quoted the tradition which he gives in regard to
MARK, the author of the Gospel. It is in the following words: "This also the presbyter said:
Mark, having become the interpreter of Peter, wrote down accurately, though not indeed in order, whatsoever he remembered of the things done or said by Christ. For he neither heard the Lord nor followed him, but afterward, as I said, he followed Peter, who adapted his teaching to the needs of his hearers, but with no intention of giving a connected account of the Lord's discourses, so that Mark committed no error while he thus wrote some things as he remembered them. For he was careful of one thing, not to omit any of the things which he had heard, and not to state any of them falsely." These things are related by Papias concerning Mark. But concerning
MATTHEW he writes as follows: "
So then Matthew wrote the oracles in the Hebrew language, and every one interpreted them as he was able." And the same writer uses testimonies from the first Epistle of John and from that of Peter likewise.
Papias lived 60-130 AD. Eusebius had his works available to quote.
Eusebius, Ecclesiastical History 3 - On the Gospel Authorship
The witness of Clement opining on the early Presbyters witness of the Gospels and mention of Papias as well (60-130AD):
On the Composition of Mark, citing Clement of Alexandria [Bishop of Alexandria in Egypt; lived ca. 150-215]:And thus when the divine word had made its home among them [the Christians in Rome], the power of Simon [the magician] was quenched and immediately destroyed, together with the man himself. And so greatly did the splendor of piety illumine the minds of PETER'S hearers that they were not satisfied with hearing once only, and were not content with the unwritten teaching of the divine Gospel, but with all sorts of entreaties
they besought MARK, a follower of Peter, and the one whose Gospel is extant, that he would leave them a written monument of the doctrine which had been orally communicated to them.
Nor did they cease until they had prevailed with the man, and had thus become the occasion of the written Gospel which bears the name of MARK. And they say that Peter when he had learned, through a revelation of the Spirit, of that which had been done, was pleased with the zeal of the men, and that the work obtained the sanction of his authority for the purpose of being used in the churches.
Clement in the eighth book of his
Hypotyposes gives this account, and with him agrees the bishop of Hierapolis named
Papias. And Peter makes mention of Mark in his first epistle which they say that he wrote in Rome itself, as is indicated by him, when he calls the city, by a figure, Babylon, as he does in the following words: "The church that is at Babylon, elected together with you, saluteth you; and so doth Marcus my son" (1 Peter 5:13). And they say that this Mark was the first that was sent to Egypt, and that he proclaimed the Gospel which he had written, and first established churches in Alexandria. (Eusebius,
Ecclesiastical History 2.15.1-2, 2.16.1)
Eusebius, Ecclesiastical History 3 - On the Gospel Authorship
On the Composition and Order of all Four Gospels, again citing Clement of Alexandria:Again, in the same books [the
Hypotyposes], Clement gives the tradition of the earliest presbyters, as to the order of the Gospels, in the following manner: "The Gospels containing the genealogies [i.e.
Matthew and
Luke], he says, were written first. The Gospel according to
MARK had this occasion.
As Peter had preached the Word publicly at Rome, and declared the Gospel by the Spirit, many who were present requested that Mark, who had followed him for a long time and remembered his sayings, should write them out. And having composed the Gospel he gave it to those who had requested it. When Peter learned of this, he neither directly forbade nor encouraged it.
But, last of all, JOHN, perceiving that the external facts had been made plain in the Gospel, being urged by his friends, and inspired by the Spirit, composed a spiritual Gospel." This is the account of Clement. (Eusebius,
Ecclesiastical History 6.14.5-7).
Eusebius, Ecclesiastical History 3 - On the Gospel Authorship
Eusebius was even a textual critic in his time:
Eusebius of Caesarea, Letter to Carpianus on the gospel canons: English translation
Ok how deep do you want to go? There’s more and the actual works of the cited bishops and theologians.