Safe Harbor for Rental Income for Qualified Business Income Deduction

Recently the IRS released additional guidance on a large number of issues related to the Qualified Business Income (QBI) Deduction (Section 199A). This deduction allows certain taxpayers who have flow thru businesses (S Corporations, partnerships, sole proprietorships) to take a 20% deduction on the related income. To qualify, the activity has to rise to the level of a trade or business. Question: is rental activity a trade or business?