From my experience, it's best to not attach a cover letter if they're not specifically asking for it. If it's not on the application page, the team is telling you they do not have time to read through everyone's cover letter. I found that cover letters almost never benefit the applicant, and I (personally) would not attach it nor spend time writing a document the HR rep might not have the time to read.
HR teams have large amounts of applicants where they spend days reading through applications. Instead of putting effort and time into a cover letter that they did not ask for, spend time perfecting your resume with a great design & great content. Make sure it allows you to stand out from the ground with an eye catching layout & list all of your experiences and skills that reflect what the organization is looking for.
And as always, stick to a 1-pager.