Added note on usage of "netplan" for Ubuntu network configuration (apache#203)

Author: Hudratronium

source/installguide/hypervisor/kvm.rst

@@ -464,6 +464,10 @@ changed to be more description.
 There are many ways to configure your networking. Even within the scope of a given 
 network mode.  Below are a few simple examples.
 
+.. note::
+   Since Ubuntu 20.04 the standard for manging network connections is by
+   using NetPlan YAML files. Please refer to the Ubuntu man pages for further
+   information and set up network connections figuratively.
 
 Network example for Basic Networks
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^