What is the meaning of "sola scriptura"? I often see "sola scriptura" used with two very different meanings.

Serendipitously, when I typed the title question, the first two "Similar questions" presented by SE were:


What is the basis for not believing sola scriptura?
Sola scriptura is Latin for "by scripture alone". ... the Bible contains all knowledge necessary for salvation.
Sola Scriptura and the Biblical Canon
The basic argument of Sola Scriptura is that all Christian teachings and traditions are to be founded in and subservient to the Bible, and in nothing else.


The first says that the Bible is sufficient, but allows for additional sources of truth.  "Scripture alone" provides everything we need to know, but not necessarily everything we can know.

The second says that the Bible is necessary, and denies the possibility of additional sources of truth.  "Scripture alone" is the only acceptable source of truth.

Depending upon one's denomination, either meaning is acceptable, but it seems strange that the one phrase should have two such different definitions.

Which one of these is a corruption of the original meaning?

Clarification:

Everyone (even atheists) will agree that of the two definitions, either, neither, but not both can be true.

Given a "new" doctrine that doesn't conflict with the Bible, the first view would say "it might be true, and it's okay to accept it, but believing or not believing it won't affect our salvation", while the second view would say "even if it is true, we should reject it for being non-Biblical".

I'm interested in knowing the original meaning, and in the history of how the meaning of "sola scriptura" changed to take on two contradictory meanings.

Summary:

The response that best answers this question is the comment containing a link to GratefulDisciple's answer to a similar question, which refers to four different definitions of Sola Scriptura as described in Keith Mathison's "The Shape of Sola Scriptura".  In particular, the differences between "Tradition 1" and "Tradition 0" are what I was asking about.  Tradition 0 corresponds to the "in nothing else" view, which Mathison calls "Solo Scriptura", with an "o" rather than an "a".
I’m not at all convinced that the two interpretations of Sola Scriptura presented in your question are definitive, let alone which one is a corruption of the original meaning.  But before we go any further, it is important to establish what “Tradition” means.  One source of information says this under the heading ‘Irenaeus and Tertullian held to sola Scriptura’:

It is with the writings of Irenaeus and Tertullian in the mid to late second century that we first encounter the concept of Apostolic Tradition (tradition handed down in the Church from the apostles in oral form). The word tradition simply means teaching.  Irenaeus and Tertullian state emphatically that all the teachings of the Bishops that was given orally was rooted in Scripture and could be proven from the written Scriptures. Both men give the actual doctrinal content of the Apostolic Tradition that was orally preached in the churches. From this, it can be seen clearly that all their doctrine was derived from Scripture. There was no doctrine in what they refer to as apostolic Tradition that is not found in Scripture.  In other words, the apostolic Tradition defined by Irenaeus and Tertullian is simply the teaching of Scripture...  The Early Church operated on the basis of the principle of sola Scriptura. It was this historical principle that the Reformers sought to restore to the Church.  Source: https://christiananswers.net/q-eden/sola-scriptura-earlychurch.html

Here are a few excerpts from an article adapted from a chapter entitled &quot;Sola Scriptura&quot; by Mark D. Thomson in Reformation Theology: A Systematic Summary, edited by Matthew Barrett.  What Did Luther Really Believe about Scriptural Authority?

Luther was summoned to an interview with Tommaso de Vio, or Cardinal Cajetan (1469–1534), following the Diet of Augsburg in October 1518. When Cajetan challenged him on the basis of the church’s teaching, Luther insisted, “The truth of Scripture comes first. After that is accepted one may determine whether the words of men can be accepted as true.” [1 Martin Luther, Acta Augustana (1518), WA 2:21.5–6; LW 31:282.]
It is clear that Luther was not dismissing the authority of “the words of men” but rather submitting them to what he regarded as a higher authority, “the truth of Scripture.” Throughout his ministry Luther would cite the fathers and the creeds and even some decisions of the early church councils in support of his teaching, but he did not consider them decisive. Yet they were also more than merely illustrative. Insofar as they faithfully expressed the teaching of Scripture, they were to be regarded as authoritative. Scripture was not the only authority but rather the final authority.
He recognized other subsidiary and contingent authorities, not alongside but under the rule of Scripture, which remained his final authority. These other authorities included not only the church fathers but also a number of significant medieval theologians.
His willingness to reason from the Scriptures (following the example of Paul in Acts 17:2) is evident as early as the famous statement made at the Diet of Worms in May 1521:6
”Unless I am convinced by the testimony of the Scriptures or by evident reason—for I can believe neither pope nor councils alone, as it is clear that they have erred repeatedly and contradicted themselves—I consider myself conquered by the Scriptures adduced by me and my conscience is captive to the Word of God.” [7 Martin Luther, Verhandlungen mit D. Martin Luther auf dem Reichstage zu Worms (1521), WA 7:838.4–7; LW 32:112.]
So for Luther, Scripture itself remained the final authority, but this did not eliminate all appeal to the fathers, the creeds, and the decisions of the church. Reading Scripture is a fellowship activity in which the voices of those who have read before us need to be heard attentively.  Source: https://www.crossway.org/articles/what-sola-scriptura-really-means/

Finally, here is an extract from an article on the Lutheran view of Sola Scriptura and Tradition:

Sola Scriptura in Lutheran form is not against tradition per se.  While some brands of Christianity might insist that if it’s not in the Bible then it’s not Christian, Lutheran theology understands that a tradition is allowable when (a) it is not contradicted by scripture, (b) it serves a purpose that is scriptural, and (c) it is not enforced as a pre-condition for Christian unity.  It is nonetheless possible to assert the principle of Sola Scriptura in a manner similar to the bumper sticker that says: “The Bible Says It, I Believe It, That Settles It.”  However, a Lutheran theological approach resists simplification.  For Lutheran Christians, reading the Bible does not mean setting aside critical thinking skills. Source: https://lutherantheology.wordpress.com/2011/01/18/a-brief-introduction-to-sola-scriptura/

To answer your question, I agree with Martin Luther who said the truth of Scripture comes first and that Scripture is the final authority.  Yes, the Bible contains all knowledge necessary for salvation as it says in 2 Timothy 3:16-17:

All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness; that the man of God may be perfect, thoroughly furnished unto all good works.  (KJV but took the liberty of replacing ‘throughly’ with thoroughly)

However, that does not mean we have to disengage our intellects or refuse to acknowledge biblical teachings (traditions) that have been handed down from the early church fathers who were taught by Jesus’ disciples.
I’m now going to track down that bumper sticker.