Hi guys! I want to ask about the same issue with my Mi 9. I checked and saw that my Widevine security level is L3. The phone has never had an unlocked bootloader, never had custom software installed, and has never been rooted — basically, no modifications have ever been made to it. It’s always been on stock firmware. I also used to have an S9, and even after unlocking the bootloader, it still kept L1. It only dropped to L3 after flashing custom software, and when I went back to stock, it returned to L1. That doesn’t explain why my Mi 9, which has never been unlocked or modified, is still stuck on L3. I just want to watch HBO Max in better quality 🙂