The LORD declared Himself to be one person the vast majority of times in the Holy Scriptures. He never referred to Himself as three persons. He referred to Himself as THE GREAT PERSON or plural intensive. The Hebrew plural intensive implies the greatness of a singular object or person.
King Jesus has appeared in human form many times in the Holy Scriptures. When He appeared to John The Revelator, He said He was the first and the last, the beginning and the end, the alpha and omega. He referred to Himself as THE ALMIGHTY GOD in the singular tense. When the prophet Isaiah saw a vision of Christ sitting on His throne, He saw one person on a single throne. Isaiah did not believe in the trinity.
The trinity came from Constantine The Great and Theodosius The Great as the result of the first and second nicene council. Neither man knew anything about Judaism or Christianity. They hybridized their pagan triad of demons with the Christian religion. So let the trinity go. It is a perversion. One person can not be three persons. Three persons can not be one person.