Do kneel-downs count as rushing attempts?

Yes. In NFL statistics, a normal quarterback kneel-down is a rushing attempt credited to the quarterback, with the corresponding yardage loss included in his rushing total.

For example, a quarterback with 20 rushing yards who takes two kneel-downs for a loss of 1 yard each finishes with 18 yards and two additional carries. This can also affect fantasy points when rushing yards are part of the league's scoring.