I dont think that asking for confirmation that an applicant has read the job advert

Honestly there are way less annoying and time consuming ways to do this for you and the applicant, like just including a line in the posting "To confirm you've read the job description, all interested applicants should apply via emailing their resume to x@y.com with the job title and location in the subject line," or something.

Cover letters are complete bullshit as they are currently used. If I were applying to a management role in a niche industry, or something in the C-suite or other positions one would only get after advancing a fair bit in their career, I can understand the point of a cover letter. When the hardware store wants a cover letter for their part-time cashier position or Taco Bell wants one for their shift manager job? They can get fucked, everything relevant to the candidate's suitability for the role ought to already be in their resume, and at that point companies are just seeing who's willing to degrade themselves the most and jump through the most hoops.

When everyone and their dog wants me to write them a cover letter telling them how it's been my lifelong dream to have chance to listen to middle-aged ladies go apeshit over some coupon not scanning right in my new post as a Joann Fabric Cashier (<12 hour per week position), I cannot be bothered with it. At this point, it's become so stupidly widespread beyond roles where it would actually be useful, I refuse to write them on principal and just assume that if a company rejected my application on that basis, they're the sort of clueless people I wouldn't want to work for anyway.