To add to the confusion, this from the recently released draft of Pub 535, pg 2. The draft is dated Jan 7. Emphasis added.
https://www.irs.gov/pub/irs-dft/p535--dft.pdf
I
In general, to be engaged in a trade or busi-
ness, you must be involved in the activity with
continuity and regularity and your primary pur-
pose for engaging in the activity must be for in-
come or profit. If you own an interest in a
pass-through entity, the trade or business de-
termination is made at that entity's level.
The ownership and rental of real property
doesn’t, as a matter of law, constitute a trade or
business, and the issue is ultimately one of fact
in which the scope of your activities in connec-
tion with the property must be so extensive as
to give rise to the stature of a trade or business.
However, the rental or licensing of property to a
commonly controlled trade or business is con-
sidered a trade or business under section 199A.