I hope you fixed the problem in theese months, here is the solution for anyone having the same problem.
In Xiaomins BIOS secure boot option is locked. You can find the option in “security”.
To unlock the option go to set a password for bios settings, once you create your password, you can disable secure boot. Then after that go to change password and put the old password but leave “new password” in blank.
Now secure boot option is again locked, but disabled instead of enabled.