In the US, things that you buy and use for your job are tax-deductible (no doubt the IRS has a very detailed definition of “use for your job”). If your employer buys them for you, then the employer gets to deduct them as a business expense.

Mortgage interest (up to a certain ceiling) is always deductible in the US, whether or not you are working from home. If a certain part of your home is set aside for business use, you can also deduct a proportional slice of your real estate taxes, depreciation, and various other things, but not, it appears, the principal.