Canonical has withdrawn the Intel Microcode update that was released on November 11 for all supported versions of Ubuntu Linux. The update had problems launching some Intel Tiger Lake systems.
New security vulnerabilities affect all Linux systems running certain Intel processors. So on November 10th, Intel launched new update for Intel Microcode on Linux systems. Updates were released along with new versions of the Linux Kernel to address these new flaws.
Canonical was fast enough to fix Intel Microcode packages on all supported versions of Ubuntu (Ubuntu 20.10, Ubuntu 20.04 LTS, Ubuntu 18.04 LTS, Ubuntu 16.04 LTS and Ubuntu 14.04 ESM).
Unfortunately, the Intel Microcode update caused problems with some processors in the Intel Tiger Lake family, causing some systems to fail to boot. So Canonical now uses the Intel Microcode update to the previous one version only for Tiger Lake processor family.
The company has informed users that they can use the Kernel dis_ucode_ldr parameter in the boot menu to disable firmware loading in the event of a malfunction.
If you are using one of the supported versions of Ubuntu in computer that uses an Intel Tiger Lake processor and you have already installed yesterday's Intel Microcode update, it is recommended that you update the system again to the new Intel Microcode version that is already in the main repositories.
If you installed yesterday's Intel Microcode update and are experiencing issues on boot, you should use the kernel command line option mentioned above (dis_ucode_ldr) to prevent the problematic firmware from loading.
Then update your system from the terminal using the commands.