rental real estate is not a SSTB - Specified service trade or business. (Nor do you want it to be a SSTB because they are subject to more limitations to qualify for the QBI deduction than non-SSTB's). if your rental activities rise to the level of a trade or business you are entitled to take the QBI deduction for the profit from those activities subject to numerous rules that can limit the deduction.
The proposed regs do not provide any supplemental guidance on the circumstances under which a rental real estate activity rises to the level of a trade or business, other than to provide a special rule for self-rental activities (allowing for such activities to be considered part of the trade or business to which tangible or intangible property is rented or licensed).