Adding stubble to Ubuntu's generic Arm64 Desktop ISOs

Tobias Heider has writtenan article that explains changes that are coming for Ubuntu's genericArm64 desktop ISO images in the 25.10 release. The current solution,Heider says, depends on GRUB features that are unavailable in secureboot mode and require adding device-specific logic to multiplepackages. The new solution, called stubble,is derived from systemd-stub:

A bundled stubble image contains stubble itself, a Linux kernel, aHWID lookup table to map devices to device trees and multiple devicetrees. When grub loads this "kernel", stubble executes first, readsthe SMBIOS table to generate HWIDs, looks for a match in the embeededlookup table and loads a matching device tree before passing controlto the actual Linux kernel.

The elegance in this approach lies in how it interacts with therest of the system. Integrating stubble happens entirely at build timein the kernel package. The stubble package is a build dependency forthe kernel. After building the kernel itself, we bundle it withstubble and our DTBs and ship the combined binary instead. Theresulting stubble + kernel + dtb bundle can be loaded by grub like anyother Ubuntu kernel. No further changes in grub or other packages arenecessary to make it work.