HI:
When restarting the MCU, if SMR verification fails, can the MCU output a signal telling me that secure boot failed
Pay attention to "S32K3xx Secure Boot Application Note" you will find as secure document on NXP webpage:
https://www.nxp.com/support/support/secure-access-rights:SEC-ACCESS
If any of the SMR verified fails verification, HSE applies the configured sanction (according pre-boot or post-boot phase) for the associated CR entry.