Your headphone crackle and screen flicker issues both sound like hardware problems. I've never experienced anything like that on any Linux machine I've ever use

Your headphone crackle and screen flicker issues both sound like hardware problems. I've never experienced anything like that on any Linux machine I've ever used. I did have an old HP laptop (running Windows) where the screen hinge had damaged the video cable, and I'd get flicker unless it was opened just right.