Not located in the USA, so no idea what triggers the IRS, but in general in other countries:Yes. And creating an LLC is cheap and easy to do. If you dedicate one room of your home to your LLC and Mac Pro, then all expenses related to that room are expenses to deduct. All office supplies you use for the LLC are deductible as well. And as you say, 'items' of any type that are legitimately used by you for your LLC and approved by the IRS are allowed. You might think that lap dance is important to the running of your LLC, but the IRS would not think so. Use common sense. An LLC structured company also shelters your family and your other life from any damages incurred by your LLC. That is a very good reason to have one. Not trying to give you business advice on a Mac Pro thread.... but a Mac Pro and XDR are allowed by the IRS for an LLC whose purpose is or has computer related business activity.
All of that implies that you have a business ... as in you have paying customers. No customers, no income, no taxes (also nothing to deduct from those taxes) and eventually questions from the taxman wanting to know what your "business" actually is.