to test your ankle range, you should do that individually and not as part of a greater movement pattern.  the test for ankle range is best done either kneeling in lunge position or with your foot up on a stool or similar. we usually like to use a pole placed straight up at the inside of the foot. then lean forward with the knee, keeping it to the outside of the pole.  this makes sure the knee drives in an optimal path that does not impinge at the ankle, nor letting the arch collapse.

if you can get the knee many inches forward of the toes without the heel coming up, then you probably have enough ankle range.  if you can’t get the knee much past the toes, then something is restricting your ankle. 

ankle dorsiflexion exercises uses the same motion as the test. move it back and forth in the same path of the test, making sure your arch does not collapse.  Kstarr likes to use a band to distract the ankle, either forward, backward or out to the side.  Find which one has the best effect for you.

the ankles may be the source of lack of ROM, but there are many structures up and down stream that could be to blame beyond the ankle itself.  you should examine the anterior tibialis, posterior tibialis, calf, heel cord, bottom of the foot, peroneals all for tightness next. so while the ROM limitation may seem like the ankle, it could be other structures that are at fault not at the ankle.

we cannot see how you’re squatting, so it’s possible that there are hip and upper leg restrictions as well as your ability to maintain bracing of the core.  you should consider all those in your search for what’s restricting you from getting to the bottom in good position.