There is a difference between looking for specific verses like Trinity and doctrines derived from the scriptures themselves. A believer in sola scriptrua would be a person that looks for doctrines to be derived from the scriptures in a clear and explicit way.
Did the Bible defined the Trinity, or did the Church Council? I’m sure you know the answer to this question. The Bible itself cannot be properly understood unless some authoritiative body like a Church to determine the truth. It was in the Council of Nicea in 325 AD that defined and declare God as three divine person. The Council did use Scripture to support this doctrine. First it was the bishop of Alexandria, Theophilus,and then Tertillian was credited to have used it. The Trinity is not explicit in Scripture.
There is no Scripture verse that describe God as Three Divine Persons but One God. Only in the Church such definition is used basing this concept from Scripture as well. There is no difference.
Likewise, the Church since around 200s believed Mary as sinless. In both in the Catholic Church and Eastern Orthodox Church as the Ark of the New Covenant.
In Catholic and Orthodox theology, the Ark of the Covenant is seen as the Old Covenant type or foreshadowing of the place of the Blessed Virgin Mary in the New Covenant. Pope Pius XII explained the connection in his apostolic constitution “Munificentissimus Deus”:
“Just as the New Covenant surpasses the Old, so the new Ark of the Covenant (Our Lady) is superior to the old. The old Ark contained the word of God inscribed on stone tablets, but the new Ark contained the Incarnate Word of God. The old Ark held the Law that could not justify, but the new Ark held Jesus Christ Who Himself is the eternal New Covenant with God; He Who justifies and saves.”
There are several direct parallels between between the Old Testament accounts of the Ark and the account of Mary in the Gospel of Luke:
The words of Ex. 40:34-38, referring to the cloud of the Lord’s presence “covering” the tent of the Ark are echoed in Gabriel’s words to Mary in Luke 1:35: “…the power of the Most High will cover you with its shadow.”
David greets the Ark in fearful awe with the words “How shall the ark of the Lord come to me?” (2 Sam.6:9); Elizabeth greets Mary with the words, “Who am I that the mother of my Lord should come to me?”
In 2 Samuel 6:10-12 the ark is sent to the hill country of Judea and stays at the household of Obededom for three months; similary, Mary journeys to Elizabeth’s house and stays there three months.
Just as David danced in the presence of the Ark (2 Sam. 6:14), the babe in Elizabeth’s womb (John the Baptist) dances in the presence of God’s Shekhinah in Mary’s womb (Luke 1:41).
Additionally, in the Book of Revelation, St. John, immediately after seeing the Ark in Heaven, sees a “woman clothed with the sun” who bears a Child “who will rule the nations with an iron rod” (Revelation 11:19-12:5; cf: Psalm 2:9).
This teaching is found in the writings of the Fathers of the Church. A sermon attributed to St. Athanasius addresses the Blessed Virgin thus: “O Ark of the new covenant, clad on all sides with purity in place of gold; the one in whom is found the golden vase with its true manna, that is the flesh in which lies the God-head.” St. Gregory Thaumaturgus wrote: “Let us chant the melody that has been taught us by the inspired harp of David, and say, ‘Arise, O Lord, into thy rest; thou, and the ark of thy sanctuary.’ For the Holy Virgin is in truth an ark, wrought with gold both within and without, that has received the whole treasury of the sanctuary” (Homily on the Annunciation to the Holy Virgin Mary).
In the Litany of the Blessed Virgin Mary, one of the titles by which Mary is addressed is “Ark of the Covenant”
Even though the sinless is not explicit in Scripture. It is implied and the Church of Christ have believed this to be true since the beginning. No early Christian believed that Mary sinned. It was not until the Protestants came into the picture.
Yes, there were ECF who say that Mary had faults, but none of the said she sinned. To consider Mary as sinful is a new doctrine.