Leap 15.6 install has lost other OS boot options

[GrandDixence2]

Your system supports UEFI Secure Boot: Use BIOS boot menu to start the operating system of your choice. Simply forget grub boot menu and os-prober.

How to get Leap 15.6 grub advanced options to show the specific kernels?

Follow this recommendations or you never leave the boot manager hell: Configure your system to boot in UEFI Secure boot mode. https://docs.oracle.com/en/operating-systems/oracle-linux/secure-boot/sboot-OverviewofSecureBoot.html#sb-overview Follow: Each operating system should have one directory on the EFI partition. One directory for TW, one for LEAP (and one for MS Windows). You will find in this directory the EFI file which contains code from the boot manager for this operating system. /…

Your system supports UEFI Secure Boot: Future SBAT updates from Microsoft could block linux boot:
https://www.heise.de/en/news/Microsoft-extends-workaround-for-Windows-SBAT-update-9848078.html

https://docs.oracle.com/en/operating-systems/oracle-linux/secure-boot/sboot-ToolsandApplicationsforAdministeringSecureBoot.html

Today:

# mokutil --sb-state
SecureBoot enabled

# mokutil --list-sbat-revocations
sbat,1,2024010900
shim,4
grub,3
grub.debian,4