Skipping acquire of configured file 'main/binary-i386/Packages'

You must change the line of /etc/apt/sources.list.d/pgdg.list to

deb [arch=amd64] http://apt.postgresql.org/pub/repos/apt/ focal-pgdg main

The definition for your apt.postgresql.org repo is defined in one of two possible places. Let's find it...

In terminal...

sudo grep -i postgresql /etc/apt/sources.list

or

sudo grep -i postgresql /etc/apt/sources.list.d/*.list

You'll get a hit on one of the above commands.

Let's edit the file...

sudo -H gedit /etc/apt/sources.list (ignore any warning messages)

or

sudo -H gedit /etc/apt/sources.list.d/found_filename.list (ignore any warning messages)

Find the line that starts with...

deb https://blah blah blah

And change it to...

deb [arch=amd64] https://blah blah blah

Save the file and quit the editor.

Now sudo apt-get update and sudo apt-get upgrade will run without the noise.

Run this command to find a /pgdg.list file

sudo -H gedit /etc/apt/sources.list.d/pgdg.list

Find the line:

*deb http://apt.postgresql.org/pub/repos/apt focal-pgdg main*

And change it to (by adding the [arch=amd64]):

deb [arch=amd64] http://apt.postgresql.org/pub/repos/apt focal-pgdg main

SAVE file and RUN

sudo apt-get update