Protestants should stick to the Bible. Their first premise, "by the Bible alone", is NOT TAUGHT BY THE BIBLE! Therefore, their instance that everything must be written down completely in the Bible IS NOT BIBLICAL. 2 Thessalonians 2:15 proves that Scripture alone IS NOT ALL THAT THERE IS.
The only Protestant churches that are close to solo scriptura are the fundamentalist bible churches.
Most Protestants would fall somewhere between sola scriptura and regula fidei as far as authority and sources of Truth for doctrine.
Even those who claim to be solo scriptura are not so in practice, as they do recognize the Trinity as proposed in the council of Nicea (325), as well as many other agreements proposed in the first four ecumenical councils that would be considered to be traditional.
It is only when the temporal Catholic Church (composed of Roman Catholic and EOC) clearly deviate from the Truth following these first four ecumenical councils that the temporal church's tradition is no longer seen as valid, and, in fact becomes quite questionable.
At this point, the Catholics (composed of Roman Catholic and EOC) began to put their trust in the episcopacy and temporal structure, as well as in manmade sacraments, and depart from the spiritual church, which is the true Church of Christ.
Jesus told Nicodemus that he must be born from above. In other words, he must be born spiritually, (John 3:3). When we enter into a relationship with Jesus Christ, we are born spiritually into His Church. Your temporal church cannot take the place of the spiritual church.
It is this spiritual church of Christ that is described in the bible.
1 Peter 2: 4 As you come to him, the living Stone--rejected by men but chosen by God and precious to him-- 5 you also, like living stones, are being built into a spiritual house to be a holy priesthood, offering spiritual sacrifices acceptable to God through Jesus Christ.
Ephesians 2: 18 For through him we both have access to the Father by one Spirit. 19 Consequently, you are no longer foreigners and aliens, but fellow citizens with God's people and members of God's household, 20 built on the foundation of the apostles and prophets, with Christ Jesus himself as the chief cornerstone. 21 In him the whole building is joined together and rises to become a holy temple in the Lord. 22 And in him you too are being built together to become a dwelling in which God lives by his Spirit.
Not the manmade one which is temporal and will not stand against the gates of Hades.