Might be ankle, might be hip, or most likely a bit of both.
Let’s see if we can eliminate the ankle first. The simplest way to release pressure on the ankle is to gradually point them out until you can get your ass down between your calves. However what I’d like you to do is stand with feet shoulder width apart, pointing straight forward and get down low as you can, lean your body weight forward if you have to.
From there lift one foot and extend your leg right in front of you (called a pistol squat). If you have enough functional strength then you should be able to get a decent balance. Don’t worry if you fall over, just try again and adjust your weight.
Now try the other leg. It’s common to be better one side than the other. The pistol position forces the weight bearing ankle to flex and adjust. Basically if you can’t do a pistol for even a few seconds then it’s ankle mobility problem.
Try it out and let me know how you get on. If it’s ankle then there are exercises that will help increase flexion and range.