Comment 2 for bug 1849566

Unpacking r8168-dkms (8.045.08-2ubuntu1) over (8.045.08-2) ...
Setting up r8168-dkms (8.045.08-2ubuntu1) ...
Loading new r8168-8.045.08 DKMS files...
Building for 5.3.0-21-generic 5.3.0-23-generic
Module build for kernel 5.3.0-21-generic was skipped since the
kernel headers for this kernel does not seem to be installed.
Building initial module for 5.3.0-23-generic
EFI variables are not supported on this system
/sys/firmware/efi/efivars not found, aborting.

Running module version sanity check.
 - Original module
   - No original module exists within this kernel
 - Installation
   - Installing to /lib/modules/5.3.0-23-generic/updates/dkms/