Ventoy is based on grub2 which is in GPL license, so it will not directly get signed with UEFI Certificate.
Like most Linux distros, Ventoy grub2 must be launched by shim when Secure Boot is enabled.
Different is that, Ventoy does not have its own shim and must make use of a third-part shim.
When boot Ventoy with Secure Boot enabled, the shim will not directly boot Ventoy grub because Ventoy grub is not signed with the shim embedded Certificate.
The shim will open the MokManager and we must enroll Ventoy's Secure Boot Key and reboot, then the shim will accept Ventoy grub and boot it.