No, generally speaking, you do not flip meat on a pellet grill. Both grills and smokers come with a lid, and you should avoid opening this lid while the meat is cooking. If you do open the lid, then this will affect the heat of the grill and, in turn, affect your meat.
When you cook meat on a grill, it is advised that you do so on a low heat for a long period of time. Slowly cooking the meat will result in a better, and tastier, finish. But, when you are dealing with low temperatures, they will be more at risk from outside forces. Such as opening the lid.
So, while you might feel like you should flip your meat when cooking it on a pellet grill, you shouldn’t do this. Instead, trust the process and wait for your meat to cook.