When I try apt-get update
I get the following error:
W: GPG error: http://deb.opera.com/opera stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4B8EC3BAABDC4346
E: The repository 'http://deb.opera.com/opera stable 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.
This also blocks me from upgrading to 20.04. I have already uninstalled Opera; did not use it much anyway.