W:Skipping acquire of configured file 'main/binary-1386/Packages' as repository... doesn't support architecture '1386' [duplicate]

I've recently started having difficulty with the Software Updater. When I try to run it, I get the message:

Failed to download repository information. Check your internet connection.

My connection is working fine, so I'm sure it must be something else. Below is the output from Details input as code, because it was the only way I could find that it would allow me to include it.

W:Skipping acquire of configured file 'main/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial InRelease' doesn't support architecture '1386', 
W:Skipping acquire of configured file 'restricted/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'main/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-updates InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'restricted/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-updates InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'multiverse/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-updates InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'main/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-backports InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'restricted/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-backports InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'universe/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-backports InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'multiverse/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-backports InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'main/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-security InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'restricted/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-security InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'universe/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-security InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'multiverse/binary-1386/Packages' as repository 'http://mirror.steadfast.net/ubuntu xenial-security InRelease' doesn't support architecture '1386', 
W:Skipping acquire of configured file 'main/binary-1386/Packages' as repository 'http://ppa.launchpad.net/fkrull/deadsnakes/ubuntu xenial InRelease' doesn't support architecture '1386',
W:Skipping acquire of configured file 'universe/binary-1386/Packages' as repository 'http://repos.codelite.org/wx3.0.3/ubuntu zesty InRelease' doesn't support architecture '1386', 
W:Skipping acquire of configured file 'main/binary-1386/Packages' as repository 'http://ppa.launchpad.net/webupd8team/java/ubuntu xenial InRelease' doesn't support architecture '1386',
W:The repository 'http://ppa.launchpad.net/pcf/miro-releases/ubuntu xenial Release' does not have a Release file.,
W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use.,
W:See apt-secure(8) manpage for repository creation and user configuration details.,
W:Skipping acquire of configured file 'main/binary-1386/Packages' as repository 'http://ppa.launchpad.net/webupd8team/tor-browser/ubuntu xenial InRelease' doesn't support architecture '1386', 
E:Failed to fetch http://ppa.launchpad.net/pcf/miro-releases/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found,
E:Some index files failed to download. They have been ignored, or old ones used instead.`

Running the following commands produced no output.

grep -i 1386 /etc/apt/sources.list
grep -i 1386 /etc/apt/sources.list.d/*.list

Solution 1:

Your computer is set up with an incorrect architecture type.

In terminal...

Lets see what we have now...

sudo dpkg --print-architecture
    # could show amd64
sudo dpkg --print-foreign-architectures # note the ending s
    # could show 1386 <-- this is the bad one

Lets fix the problem...

sudo dpkg --remove-architecture 1386 # delete the bad one
sudo dpkg --add-architecture i386 # add a good one

Update #1:

The error E:Failed to fetch http://ppa.launchpad.net/pcf/miro-releases/ubuntu/dists/xenial is because no xenial repository exists.

In terminal...

cd /etc/apt/sources.list.d
grep -i miro-releases *.list
    # note the filename that is returned
gksudo gedit /etc/apt/sources.list.d/{enter found filename here}
    # comment out the deb lines by placing a # at the beginning of the lines
    # save the file and quit gedit