Postgres upgrade trouble

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/10/static/pgupgrade.html
Description:

This is a non IT specialist question / comments. I like postgres, except the
current automatic upgrade mechanism working on my server...
On my Ubuntu 16.04 machine, when a postgres upgrade comes and installs
automatically, this creates a real nightmare: neither pgAdminIII not my
application can access the DB. (connection refused. Is the server running...
...on port 5432?)
Trying to understand in the documentation what to do is very difficult
because there is no clear example on how to retreive the 'old' or 'new'
parameters. So, I wonder why there is no automatic mechanism coming with the
upgrade to change the settings automatically, or alternatively to keep the
'old' version up and running correctly (and in this case the end user should
have an easy way to know that he has to launch an upgrade when he wants to,
and an utility -for instance in pgAdmin- should guide him along this upgrade
mechanism, ensuring I do not loose time nor any data).
Thanks for your efforts to offer Postgres to the IT community!