Hello student cut off vary every year on various factors like the level of question in the entrance examination and total number of applicants in that examination. As per previous year records its expected that you need to secure rank around 6500 to get admission in IIIT lucknow. You need to secure above 97 percentile minimum.
For more updates refer to the link mentioned below - https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-cutoff-for-iiit-lucknow/amp
Feel free to comment if you have any doubt
Good luck
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