Problem:
When you run apt update, you see the following error message:
Err:12 http://packages.cloud.google.com/apt gcsfuse-bionic InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B53DC80D13EDEF05
Solution:
Install the Google Cloud key using
curl -fsSL https://packages.cloud.google.com/apt/doc/apt-key.gpg| gpg -o /usr/share/keyrings/kubernetes-archive-keyring.gpg --dearmor
After that, you can try running
sudo apt update
again.