Ubuntu – Xenial i386 sources

I have a normal sources list:

$ cat /etc/apt/sources.list
deb http://ports.ubuntu.com/ xenial main restricted universe multiverse
deb-src http://ports.ubuntu.com/ xenial main restricted universe multiverse

deb http://ports.ubuntu.com/ xenial-updates main restricted universe multiverse
deb-src http://ports.ubuntu.com/ xenial-updates main restricted universe multiverse

deb http://ports.ubuntu.com/ xenial-security main restricted universe multiverse
deb-src http://ports.ubuntu.com/ xenial-security main restricted universe multiverse

deb http://ports.ubuntu.com/ xenial-backports main restricted universe multiverse
deb-src http://ports.ubuntu.com/ xenial-backports main restricted universe multiverse

But I get these errors when apt updating:

W: The repository 'http://ppa.launchpad.net/kernel-ppa/ppa/ubuntu xenial Release' does not have a Release file.
E: Failed to fetch http://ppa.launchpad.net/kernel-ppa/ppa/ubuntu/dists/xenial/main/binary-armhf/Packages  404  Not Found
E: Failed to fetch http://ports.ubuntu.com/dists/xenial/main/binary-i386/Packages  404  Not Found [IP: 91.189.88.150 80]
E: Failed to fetch http://ports.ubuntu.com/dists/xenial-updates/main/binary-i386/Packages  404  Not Found [IP: 91.189.88.150 80]
E: Failed to fetch http://ports.ubuntu.com/dists/xenial-security/main/binary-i386/Packages  404  Not Found [IP: 91.189.88.150 80]
E: Failed to fetch http://ports.ubuntu.com/dists/xenial-backports/main/binary-i386/Packages  404  Not Found [IP: 91.189.88.150 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.

The errors make sense because they're not in the actual directory: http://ports.ubuntu.com/dists/xenial-backports/main/ But how else am I supposed to get i386 packages? If I'm using an install script for dependencies and it fails, does it mean the script needs to update its packages to use :i386 at its end?

Is this something to change in my sources list or am I using a bad mirror? How can I fix this from CLI?