4K problem and U21 chip identification

After thermal grease replacement my xbox cant work in autodetect mode (So i cant play in 4k with HDR and freesync). I have replaced TDP158 but it doesn’t helped me. I think I found the reason because U21 chip is broken. Unfourtently I cant identify what is it and where I can buy it.
Could you please help me?
You can find pictured of the broken chip by url imgur. com/a/H92tunl