Just curious if there's any methods to check bootloader state besides using fastboot. I ask because on my device, even after unlocking successfully, the bootloader still shows that its locked when using the fastboot OEM device-info command. I know it was actually unlocked because I installed a custom ROM. I relocked after install but since it seemed to be inaccurate before I want to make sure it's locked.
Yes there is...
Step 1 : Open your device’s dialer (App where you enter telephone numbers to call someone).
Step 2 : Dial the below code, it will automatically open a new windows. (if it doesn’t open a service information window on your device, you can often only access the status via fastboot)
Step 3 : Now in that window go to Service Info >> Configuration, and see if there is :
Bootloader unlock allowed - Yes
Bootloader Unlocked - Yes
Summarized from : How to Check if your Bootloader is Locked or Unlocked