How to fix update error “Clearsigned file isn’t valid, got ‘NOSPLIT’ (does the network require authentication?)”?

Suddenly sudo apt update is not working anymore on my Ubuntu 18.04.6 machine. I get the following error:

Hit:1 https://download.docker.com/linux/ubuntu bionic InRelease
Get:2 http://us.archive.ubuntu.com/ubuntu bionic InRelease
Err:2 http://us.archive.ubuntu.com/ubuntu bionic InRelease
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:3 http://us.archive.ubuntu.com/ubuntu bionic-security InRelease
Err:3 http://us.archive.ubuntu.com/ubuntu bionic-security InRelease
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:4 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease
Err:4 http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Reading package lists... Done
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://us.archive.ubuntu.com/ubuntu bionic InRelease' is not signed.
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/bionic-security/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://us.archive.ubuntu.com/ubuntu bionic-security InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://us.archive.ubuntu.com/ubuntu bionic-updates InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

My /etc/apt/sources.list:

###### Ubuntu Main Repos
deb http://us.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse

###### Ubuntu Update Repos
deb http://us.archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse

My /etc/resolv.conf:

nameserver 1.1.1.1

I have tried changing the repository mirror to no luck. I tried running sudo apt update from within an Ubuntu docker image and the same error comes out. Would this mean that this is a network issue? Or I can still do/check something?

Thanks!