I'm a fairly heavy gym-goer and feel pretty good with my deadlifting as of late, but I still have issues with my mobility when squatting. I keep listing to one side which is preventing me from progressing. My PT has been recommending mobility warm ups/exercises to do before my set...but I'm also just sooo lazy when it comes to doing them so I just...never do them. I should try and fit them in before I go to the gym so I don't have to worry about them once I get there.
Yoga is another option for you. My squatting mobility definitely improved when I was consistent with going to a weekly class, but YouTube at home is just as good. Consistency is key though, any improvements fade away if you don't keep at it.