How to improve ankle mobility?
Completely changed the game for my squats, with instant results. I incorporate them (along with a similar hip mobilization drill) before all of my squat workouts. Highly recommended.
In my case, I thought that ankle mobility is my problem but after working on my ankles for several months I didn't see the huge improvement I expected, and only then I realized that I have other mobility deficiencies such as hip flexion and rotation and my spine.
If you are not sure what your problem is, you should hire and expert for an assessment. A lot of the stuff you find online is great, but only if you exactly know what you're looking for.