If one is to formulate a doctrine that all doctrines must be found in the text, then that doctrine of sola scriptura, if it is not in the text, is logically self-defeating.
Interestingly, I can’t find the words “sola” or “scriptura” anywhere in the bulwark of Reformed doctrine, the Westminster Confession. However, there is this:
“The supreme judge by which all controversies of religion are to be determined, and all decrees of councils, opinions of ancient writers, doctrines of men, and private spirits, are to be examined, and in whose sentence we are to rest, can be no other but the Holy Spirit speaking in the Scripture.”
But…there’s this as well:
“The whole counsel of God concerning all things necessary for his own glory, man’s salvation, faith and life, is either expressly set down in Scripture… Nevertheless, we acknowledge …
that there are some circumstances concerning the worship of God, and government of the Church, common to human actions and societies, which are to be ordered by the light of nature, and Christian prudence, according to the general rules of the Word, which are always to be observed.”
In other words - the Liturgical calendar (including Lent), the Creeds, Christmas trees, Easter eggs (not bunnies - because bunnies have nothing to do with eggs), credit cards, self driving cars, etc. are not in the Bible. However - Reformed Protestants practice and use such things because we don’t believe them to be in conflict with Holy Scripture.