Oh, but I did. Unless you can show me a non-Latin MS containing the verse prior to around 400 AD, I will stand upon my ground.
But, you have just agreed that the discussion goes all the way back to (in your words) “around 400.”
Jerome’s Vulgate was when? So the discussion goes back ‘til then. In fact, the discussion goes back to the earliest appearance of the discussion of the Trinity, which was current with Tertullian, so therefore, must have preceded even him.