How to update from webupd8 team PPA (Oracle JDK 8/9) that got inconsistent with its GPG key?

This command should do the trick:

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

Have a nice day

Software and updates -> other software -> remove webupd8team PPA.

sudo add-apt-repository ppa:webupd8team/java

sudo apt-get update

worked for me.

I think you all are missing the underlying problem.... The PPA no longer works:

root@ced-looker1:/etc/apt/sources.list.d# add-apt-repository ppa:webupd8team/java The Oracle JDK License has changed for releases starting April 16, 2019.

The new Oracle Technology Network License Agreement for Oracle Java SE is substantially different from prior Oracle JDK licenses. The new license permits certain uses, such as personal use and development use, at no cost -- but other uses authorized under prior Oracle JDK licenses may no longer be available. Please review the terms carefully before downloading and using this product. An FAQ is available here: https://www.oracle.com/technetwork/java/javase/overview/oracle-jdk-faqs.html

Oracle Java downloads now require logging in to an Oracle account to download Java updates, like the latest Oracle Java 8u211 / Java SE 8u212. Because of this I cannot update the PPA with the latest Java (and the old links were broken by Oracle). For this reason, THIS PPA IS DISCONTINUED (unless I find some way around this limitation).