Greek yogurt is one of those foods that fall into a gray area with the keto police. I just yesterday found some for the first time made with whole milk. It actually gets about 1/2 of its calories from fat where most yogurts on the market including Greek are 0% fat.
As far as the carbs. The sugars are alledgedly partially consumed in the fermentation process. I’ve not seen to what degree. My vote is to buy Whole Milk Yogurt if available. Make sure it is plain with no added fruits. And enjoy it in moderation.
I found Meijer store brand and Chobani in the whole milk Greek version.