Manual action needed to resolve boot failure for Fedora Atomic Desktops and Fedora IoT
Quoting: Manual action needed to resolve boot failure for Fedora Atomic Desktops and Fedora IoT - Fedora Magazine —
On Fedora Atomic Desktops and Fedora IoT systems, the components that are part of the boot chain (Shim, GRUB) are not (yet) automatically updated alongside the rest of the system. Thus, if you have installed a Fedora Atomic Desktop or a Fedora IoT system before Fedora 40, it uses an old versions of the Shim and bootloader binaries to boot your system.
When Secure Boot is enabled, the EFI firmware loads Shim first. Shim is signed by the Microsoft Third Party Certificate Authority so that it can be verified on most hardware out of the box. The Shim binary includes the Fedora certificates used to verify binaries signed by Fedora. Then Shim loads GRUB, which in turn loads the Linux kernel. Both are signed by Fedora.