Without copy of the newspaper's rules to hand (which don't appear to be available online), it's impossible to give a definitive answer.
However newspapers always exclude NI residents from participation in prize
draws, as to allow them to do so would fall foul of the provisions of Section IV of the Betting, Gaming, Lotteries and Amusements (Northern Ireland) Order 1985 (as amended).
e.g. see here
https://creative.dailymail.co.uk/you/2022/09-mailplus/terms.html
and here
https://www.mymail.co.uk/pages/giveaway-terms
My guess is that the publishers include a similar provision in all of their competition rules as, even if there is a requirement to solve some sort of a puzzle, the ultimate winner is still determined by a random draw from all of those who've successfully done so and they're simply not prepared to risk contravening the NI legislation. (Sorry!).