MPPT for a load whose operating voltage is nearly equal to the solar panel's open circuit voltage
Yes it is. The MPPT converter will undoubtedly find a maximum power point that will lower the panel voltage. However, the boost circuit will raise this voltage to the specified voltage for the load.

What is unknown from your description, however, is if there will be sufficient current to fully power the load.

You asked about a buck converter alone. Since applying a load to the solar panel will lower its open circuit voltage, a buck converter will not help in this case. A boost converter will be needed. By itself, a boost converter may work to some degree but it depends on many factors so it may not prove reliable under conditions of varying sunlight and loads.