Depth here is worse than in the other video you posted. Doing some mobility work could help with that, you an check Squat University. The main thing I would recommend is doing goblet squat stretches on days you don’t squat. You can do this at home holding something heavy in your hands, the main idea is to give you some sort of counterbalance.
The stretch is like this: sit down into a full squat (or as deep as you can go at that moment) for 10 seconds, then push your knees out and squeeze you glutes, hold that for 10 seconds, then sit back down (should be deeper this time) for 10 sec. again. Do that for 3-5 rounds each time, I usually do a few goblet squats (like 8-10 reps) after I’m done with stretching. Other than that, some hip internal/external rotation stretches could help (look these up) as well as stretching your calves.
Another thing, since flexibility could be a limiting factor but likely you are also weak at the bottom of the squat, you could do some pause squats. A few sets of 3-6 reps, you don’t need to push close to failure and just pause for about 1-2 seconds, this should help as well.