Microsoft Has Complicated Booting Linux
See also: We Were Right All Along and the Collaborators of Microsoft Helped Competition Crimes of Microsoft
Now:
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Verifying shim SBAT data failed: Security Policy Violation - Linux Mint Forums
Note that Windows says this update won't apply to systems that dual-boot Windows and Linux. This obviously isn't true, and likely depends on your system configuration and the distribution being run. It appears to have made some linux efi shim bootloaders incompatible with microcrap efi bootloaders (that's why shifting from MS efi to 'other OS' in efi setup works.
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openSUSE:UEFI - openSUSE Wiki
This section is a step by step for resetting SBAT efi variable (aka. SbatLevelRT). Before resetting SBAT to original mode, please aware that you need to take the security risk because old shim has security issues. That's why we use SBAT mechanism to block old shim.