The merger origin long GRB 211211A was a class (re-)defining event. A precursor was identified with a  ~1s separation from the main burst, as well as a claimed candidate quasi-periodic oscillation (QPO) with a frequency ~20 Hz. Here, we explore the implications of the precursor, assuming the quasi-periodicity is real. The precursor variability time-scale requires relativistic motion with a Lorentz factor ⁠, and implies an engine-driven jetted outflow. The declining amplitude of the consecutive pulses requires an episodic engine with an ‘on/off’ cycle consistent with the QPO. For a black-hole central engine, the QPO can have its origin in Lense–Thirring precession of the inner disc at ~6−9 r_g (gravitational radii) for a mass  , and   for and dimensionless spin ⁠. Alternatively, at a disc density of ~10⁸⁻¹² g cm⁻³⁠, the required magnetic field strength for a QPO via magnetohydrodynamic effects will be of the order of B ~ 10¹²⁻¹⁴ G. If the central engine is a short-lived magnetar or hypermassive neutron star, then a low-frequency QPO can be produced via instabilities within the disc at a radius of  ~ 20–70 km, for a disc density ∼ 10⁹⁻¹² g cm⁻³ and magnetic field  G. The QPO cannot be coupled to the neutron star spin, as the co-rotation radius is beyond the scale of the disc. Neither engine can be ruled out – however, we favour an origin for the precursor candidate QPO as early jet–disc coupling for a neutron star–black hole merger remnant with mass ⁠.