I think this varies between jurisdictions. I believe it is deductible in the USA, but not here in the People's Republic of Kanuckistan, although there are ways around the limitation, depending on your appetite for the risk of a drawn-out battle with the Canada Revenue Agency.

Up here, home mortgage interest is only deductible if the home is used to generate income, so it does not apply to people who use a home as their primary residence. But what if you have a home office? What if you use it as an AirBnB some of the time?

If you ask a tax accountant whether Canadian home mortage interest is deductible, they will answer "a definite maybe." But it's actually "no" for most people who don't structure their home ownership around qualifying for a deduction.