VenToy USB
If you are using Ventoy, the solution is in the official documentation (also mentioned on this issue).
Press OK, Press any key to perform MOK management, Enroll key from disk, VTOYEFI, ENROLL_THIS_KEY_IN_MOKMANAGER.cer, Continue, Yes, Reboot.
boot - Verification failed: (0x1A) Security Violation while installing Ubuntu - Ask Ubuntu