Guide: https://droidwin.com/how-to-check-boo...
In this video, we will show you five different methods through which you could check the current bootloader status on your Android device, i.e. whether it is locked or unlocked. The first two methods could be carried out right from the Developer Options itself whereas the next three methods require your interaction with the Fastboot Mode.
00:00 OEM Unlock Status
01:26 Device Unlock Status
02:16 Fastboot Mode
04:11 Fastboot oem device-info [locked bootloader]
05:45 Fastboot getvar unlocked [locked bootloader]
06:28 Fastboot oem device-info [unlocked bootloader]
08:17 Fastboot getvar unlocked [unlocked bootloader]