Orientation of Orbi routers and satellites

I believe the answer is "omnidirectional" in the horizontal plane, and "weird" in the vertical plane:

(From https://www.l-com.com/images/downloadables/white-papers/Selecting-the-Right-Wifi-Antenna-for-your-application.pdf )

Standing up (or upside down) is the expected orientation.  Lying on the side would be the poorest.

User facing 2.4G/5G antennas for Orbi routers/satellites are mounted in (approximately) a vertical orientation.  For example, the four user facing antennas of the 750 series look like this:

(The four 5G backhaul antennas are mounted at the top of the case and are tilted.)

These antennas appear to be a typical dipole construction:

The radiation pattern for dipole antennas depends on exactly how they are constructed and what fraction of the radio wavelength they are (full wave, half wave, quarter wave, etc.).  The most common description of the radiation pattern for a dipole antenna is a "donut"

Thus, exactly above or below the antenna would have the lowest strength