Wiki indicates they made it to the 2nd group stage of the CL proper in 2002-2003, playing Barca, Inter and Leverkusen.
I'm no football expert, but those opposing clubs rarely frequent the qualifying rounds.
UEFA (non-Wiki) confirmation at
https://www.uefa.com/uefachampionsleague/history/seasons/2002/
Newcastle finished 3d in Group A, failing to advance