AvatarSophie Ker

As a baseline prescription, which are really lame and not a good way to go about mobility, I’d say the two biggest movers for the squat would be the couch stretch and the “pigeon pose”-style hip opener. A solid five minutes per leg in each other those, test-retest, should improve your squat. Doing those every single day will take you place.

Then come ankles. They take a long while to improve. I have pretty weak ankles, but with oly shoes on I can squat feet together just fine, so clearly you’re missing a lot of range here. Spend time with a band on the ankles. Like, a lot of time, ie. 5-10 minutes a foot.
Also, form: try the same width, but feet with straight. At the top, squeeze your butt, “screw your feet into the ground” or “spread the floor,” and hold that tension throughout the movement. At the bottom of the squat you should still feel like your butt is working the hardest. The lumbar reversal is most likely a lack of hip flexion; I find that the banded hip/hamstring floss (where you bend over and straighten the leg repeatedly) works well for this.