I suggested using flour because most people already have G F flour in the house for baking pies and rolls. It probably won't be much of an added expense.
A bit of flour and butter whisked into a roux is then added to the hot drippings and hot stock and honestly, that has never caused any clumping in the gravy I have made for over 30 years. ( all -purpose G F Flour now or Gold Medal back in the day)
But, all cooks have their preferences.