Third, if you don't know what the ECFs taught about the Biblical praxis of sola scriptura, then you're ignorant of church history:
Augustine of Hippo: "This Mediator (Jesus Christ), having spoken what He judged sufficient first by the prophets, then by His own lips, and afterwards by the apostles, has besides produced the scripture which is called canonical, which has Paramount Authority, and to which we yield assent in all matters of which we ought not to be ignorant, and yet cannot know of ourselves." (Augustine of Hippo, City of God, Book 11, Chapter 3)
Cyril of Jerusalem: This seal have thou ever on thy mind; which now by way of summary has been touched on in its heads, and if the Lord grant, shall hereafter be set forth according to our power, with Scripture-proofs. For concerning the divine and sacred Mysteries of the Faith, we ought not to deliver even the most casual remark without the Holy Scriptures: nor be drawn aside by mere probabilities and the artifices of argument. Do not then believe me because I tell thee these things, unless thou receive from the Holy Scriptures the proof of what is set forth: for this salvation, which is of our faith, is not by ingenious reasonings, but by proof from the Holy Scriptures (A Library of the Fathers of the Holy Catholic Church (Oxford: Parker, 1845), The Catechetical Lectures of S. Cyril 4.17).
Gregory of Nyssa: "The generality of men still fluctuate in their opinions about this, which are as erroneous as they are numerous. As for ourselves, if the Gentile philosophy, which deals methodically with all these points, were really adequate for a demonstration, it would certainly be superfluous to add a discussion on the soul to those speculations, but while the latter proceeded, on the subject of the soul, as far in the direction of supposed consequences as the thinker pleased, we are not entitled to such license, I mean that of affirming what we please; we make the Holy Scriptures the rule and the measure of every tenet (dogma); we necessarily fix our eyes upon that, and approve that alone which may be made to harmonize with the intention of those writings." (Philip Schaff and Henry Wace, Nicene and Post-Nicene Fathers (Peabody: Hendrikson, 1995), Second Series: Volume V, Philosophical Works, On the Soul And the Resurrection, p. 439).
Gregory of Nyssa: Let the inspired Scriptures then be our umpire, and the vote of truth will be given to those whose dogmas are found to agree with the Divine words. (On the Holy Trinity NPNF, p. 327)
Basil the Great, Bishop of Caesarea: "Enjoying as you do the consolation of the Holy Scriptures, you stand in need neither of my assistance nor of that of anybody else to help you comprehend your duty. You have the all-sufficient counsel and guidance of the Holy Spirit to lead you to what is right" (Philip Schaff and Henry Wace, Nicene and Post-Nicene Fathers (Peabody: Hendrikson, 1995), Second Series: Volume VIII, Basil: Letters and Select Works, Letter CCLXXXIII, p. 312).
Basil the Great: We are not content simply because this is the tradition of the Fathers. What is important is that the Fathers followed the meaning of the Scripture. (On the Holy Spirit, 7.16)
Augustine: This Mediator: [Jesus Christ], having spoken what He judged sufficient first by the prophets, then by His own lips, and afterwards by the apostles, has besides produced the Scripture which is called canonical, which has paramount authority, and to which we yield assent in all matters of which we ought not to be ignorant, and yet cannot know of ourselves. (City of God, book XI, Chapter 3, )
Augustine: Better far that I should read with certainty and persuasion of its truth the Holy Scripture, placed on the highest (even the heavenly) pinnacle of authority, and should, without questioning the trustworthiness of its statements, learn from it that men have been either, commended, or corrected, or condemned, than that, through fear of believing that by men, who, though of most praiseworthy excellence, were no more than men, actions deserving rebuke might sometimes be done, I should admit suspicions affecting the trustworthiness of the whole oracles of God. (Letters of St. Augustine, Letter 82.2.5)
Augustine: Many false Christs and false prophets shall arise, and shall do many signs and wonders, that they may deceive, if it were possible, the very elect: behold, I have told you before. This shows that the established authority of Scripture must outweigh every other; for it derives new confirmation from the progress of events which happen, as Scripture proves, in fulfillment of the predictions made so long before their occurrence. (Reply to Faustus the Manichaean 13.5)
Augustine: Neither dare one agree with catholic bishops if by chance they err in anything, but the result that their opinion is against the canonical Scriptures of God. (De unitate ecclesiae, 10)
Irenaeus: We have learned from none others the plan of our salvation, than from those through whom the gospel has come down to us, which they did at one time proclaim in public, and, at a later period, by the will of God, handed down to us in the Scriptures, to be the ground and pillar of our faith. (Against Heresies 3.1.1)
Clement of Alexandria: But those who are ready to toil in the most excellent pursuits, will not desist from the search after truth, till they get the demonstration from the Scriptures themselves. (The Stromata, 7:16)
[Notice the final court of appeal is the Scriptures, not the church. The those who are encouraged to toil in the most excellent pursuits do not refer to the church ecclesiastical authority, but to all people. All people are encouraged here to search for truth and find it finally in the Scriptures.]
Athanasius: The holy and inspired Scriptures are fully sufficient for the proclamation of the truth. (Against the Heathen, 1:3 )
Ambrose: For how can we adopt those things which we do not find in the holy Scriptures? (On the Duties of the Clergy, 1:23:102)
Consider the Council of Jerusalem described in the Acts of the Apostles. The council resolved a controversy between Pharisee converts and Paul about whether gentile converts needed to be circumcised. In the discussion, James quotes the Greek Old Testament about gentiles seeking the Lord.
. . .that the rest of mankind may seek the Lord,
Even all the Gentiles who are called by My name,
Says the Lord who does all these things. Acts 15:17 NKJV / Amos 9:12 LXX
The modern Hebrew text says something much different. It says that the gentiles will be possessed by the House of Israel.
That they may possess the remnant of Edom,
And all the Gentiles who are called by My name,”
Says the Lord who does this thing. Amos 9:12 NKJV
According the doctrine of sola scriptura, the apostles were quoting the wrong text as scripture.
Actually, chapters and verses were not assigned to scripture until long after the apostles.
Worse yet, the Hebrew text does not support the conclusion reached by the apostles. If anything, it supports the position of the Pharisees.
A few verses later, it is clear that the Holy Spirit spoke through the council. The conclusion was not a matter for personal interpretation.
For it seemed good to the Holy Spirit, and to us, to lay upon you no greater burden than these necessary things . . . Acts 15:28
The New Testament supports the authority of the Greek LXX over the Hebrew, and it supports the authority of church councils to decide controversies. In both cases, the New Testament effectively refutes the doctrine of sola scripture.
If you think this refutes the Biblical praxis of sola scriptura, then I don't think you know what sola scriptura is.