There are many conflicting opinions about who Ollamh Fodhla was and the controversy results from wrong assumptions made because of dates that have been purposely made to seem to be in conflict.
Under the latin dating-system (A.M.), presumably created by the latin catholic church, there are historical accounts of Ollamh Fodhla existing hundreds of years before the known Biblical dates of Jeremiah the Bible Prophet.
The latin dating of Ollamh Fodhla is calculated from the Creation which they date as being 5199 B.C. and they state that in 1828 BC (really c. 633 B.C.) Eochaidh "Ollothair" (all-father) mac Duach, the Daighda, became high-king.
The Bible states that The Creation was in 4004 B.C. and that Jeremiah left Jerusalem (with Zedekiah's daughter - Tea Tephi; the "Stone of Destiny" and The Ark of The Covenant) in c. 588 B.C. The date of Ollamh Fodhla's death is recorded, cut in stone, inside Cairn T, as being the 21st of Sept. in 581 B.C.
British, Irish and Scottish records of the "Stone of Destiny" locate it at Tara, Ireland in circa 500 B.C. and that Eochaidh, the Daighda, married Teia Tephi.
Ollamh Fodhla is reported to have been a king who ruled Ireland for 40 years under just Laws. Jeremiah brought The Torah (God's Laws) to Ireland and taught Eochaidh "Ollothair" to administer it from Tara and so Eochaidh inherited the title "Ollamh Fodhla" from Jeremiah, his teacher, upon his death. Their living at the same time and one continuing the other's work, led to them being confused, as being the same person, in the minds of history students.
The incorrect latin dating favoured by many catholic historians, some of whom were priests, and by like-minded archaeologists; most of whom like to contradict God and the Holy Bible; has led to this unnecessary confusion and it has been done purposely to hide the Truth that the Irish people are Israelites.
So we are left with the age-old dilemma of: Who do we believe? God or historians; priests; archaeologists and scientists? I recommend you to choose God because, unlike all of them, He is never wrong. Amen - JAH.