N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
Do you want to accept these changes and continue updating from this repository? [y/N]

A simple fix for this is to either:

Run the following and manually answer y when asked to confirm the relevant changes
Note: this is NOT apt-get, but rather just standalone apt

sudo apt update

Run apt-get update with the --allow-releaseinfo-change flag to automatically confirm the changes for you:

sudo apt-get update --allow-releaseinfo-change