Skipping acquire of configured file 'multiverse/binary-1386/Packages' as repository 'http://archive.ubuntu.com/ubuntu focal-security InRelease' doesn't support architecture '1386'

C++
sudo dpkg --remove-architecture 1386 # delete the bad one
sudo dpkg --add-architecture i386 # add a good one
sudo dpkg --print-architecture
    # could show amd64
sudo dpkg --print-foreign-architectures # note the ending s
    # could show 1386 <-- this is the bad one
Source

Also in C++: