Another form of squatting are Sumo squats, with a extra wide foot spacing. Try holding the extreme bottom position for 2 or 3 seconds, which can affect the pelvic/hip and spine. Higher reps at first, looking for that full stretch in the lower position, which in a way can be like an adjustment for the pelvic/hips/spine. Might try using just the bar, at first, to get use to the full bottom position and the extreme stretch you can get with that.
Also the Sumo DL. but for most it may take time to learn the correct form. In this regard, would suggest only doing the Sumo squat versions as a starting off point. The old Jefferson lift (little used today...akin to a DL) requires a much wider than normal foot spacing, and a very good exercise for stretching the pelvic/hip/spine complex. Change hand placings each set; one set right hand in front, next set...left hand in the front...etc, etc, etc..
OH's (overhead) squats (as chaos suggest) can really put a stretch on the whole body. Wide foot stance and low positions see to that. Total upper and lower body flexibility and stretch, a great movement. Though somewhat difficult for most to learn the correct timing and form. if wanting to invest the time to learn, than that will be to your great advantage.
Good Luck.