Comment 17 for bug 1874953

The version of less from focal-proposed resolved the issue and I'm now able to view the diff.

Configuration file '/etc/default/smartmontools'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
   What would you like to do about it ? Your options are:
    Y or I : install the package maintainer's version
    N or O : keep your currently-installed version
      D : show the differences between the versions
      Z : start a shell to examine the situation
 The default action is to keep your current version.
*** smartmontools (Y/I/N/O/D/Z) [default=N] ? d
--- /etc/default/smartmontools 2020-07-01 15:02:20.945403642 -0700
+++ /etc/default/smartmontools.dpkg-new 2019-10-09 17:32:47.000000000 -0700
@@ -4,9 +4,6 @@
 # List of devices you want to explicitly enable S.M.A.R.T. for
 # Not needed (and not recommended) if the device is monitored by smartd
 #enable_smart="/dev/hda /dev/hdb"
-enable_smart="/dev/vda"
-# uncomment to start smartd on system startup
-#start_smartd=yes

 # uncomment to pass additional options to smartd on startup
 #smartd_opts="--interval=1800"

Configuration file '/etc/default/smartmontools'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
   What would you like to do about it ? Your options are:
    Y or I : install the package maintainer's version
    N or O : keep your currently-installed version
      D : show the differences between the versions
      Z : start a shell to examine the situation
 The default action is to keep your current version.
*** smartmontools (Y/I/N/O/D/Z) [default=N] ? z
Useful environment variables:
 - DPKG_SHELL_REASON
 - DPKG_CONFFILE_OLD
 - DPKG_CONFFILE_NEW
Type 'exit' when you're done.
root@clean-xenial-amd64:/# apt-cache policy less
less:
  Installed: 551-1ubuntu0.1
  Candidate: 551-1ubuntu0.1
  Version table:
 *** 551-1ubuntu0.1 500
        500 http://ubuntu.osuosl.org/ubuntu focal-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     551-1 500
        500 http://ubuntu.osuosl.org/ubuntu focal/main amd64 Packages