Missing libc6 Dependency for a new Kernel

TL;DR: Upgrade your system to 21.10 or wait for 22.04 to be released; Kernel 5.16 is unstable.

There are two problems, libc6 and libssl3.

• libc6: libc6 version 2.34 is only available in Ubuntu 21.10. The kernel 5.16 cannot run without this library.

• libssl3: Ubuntu mainline kernel 5.15.7+ and 5.16 bumps the requirement from libssl1.1 (>= 1.1.0) to libssl3 (>= 3.0.0~~alpha1). However, package libssl3 is not available for Ubuntu 21.10 impish indri.. It's only available for Ubuntu 22.04 jammy jellyfish which is not yet released.

After reading the above we can conclude that one can NOT install kernel 5.16 on Ubuntu 20.04 LTS focal fossa.

Don't want to lose hope? There are a few things to try.

• Most of the drivers from 5.16 are also available in 5.13.9, you can try installing that kernel.

• Upgrade to Ubuntu 21.10

• Upgrade to Ubuntu 22.04

• There is a PPA for mainline kernels available for LTS. If you'd like to test the PPA then run the following commands:

  sudo add-apt-repository ppa:tuxinvader/lts-mainline
  sudo apt update
  

  Install the kernel:

  sudo apt update
  sudo apt install linux-5.16.2
  sudo apt -f install
  

• You may try installing all the packages manually from deb files but they may fully break, It may convert your system to a toaster! Don't go for that.

• The only thing to try is temporarily adding the Jammy repositories and manually installing the correct version of packages. But Jammy repositories are unstable and they may also convert your system to a toaster!

N.B: If you're using NVIDIA graphics cards, your drivers may fail to compile. Kernel 5.16 is mainline and pretty unstable. Make sure to have a backup before doing something that can convert your system into a toaster ;)

_{"toaster" means it can make your system unopertable. Just like using Linux on a toaster.}