Canonical has pulled the Intel Microcode update released on November 11 for all supported versions of Ubuntu Linux. The update featured problems on booting some Intel Tiger Lake systems.
New gaps security affect all Linux systems running certain Intel processors. So on November 10, Intel released a 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 for some processors in the Intel Tiger Lake family, so some systems could not start. So Canonical now uses the Intel Microcode update in the previous version only for the Tiger Lake family of processors.
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 on a computer running an Intel Tiger Lake processor and you already have yesterday's Intel Microcode update installed, it is recommended that you update the system again at new edition Intel Microcode that already exists in the main repositories.
If you installed the Intel Microcode update yesterday and are having issues booting, you should use the kernel command line option above (dis_ucode_ldr) to prevent the firmware from loading with problems.
Then update your system from terminal using the commands.
sudo apt update && sudo apt full-upgrade
