Question : W: GPG error: http://dell.archive.canonical.com focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D4D1EAED36962F69 NO_PUBKEY F9FDA6BED73CDC22
Answered by : purple-team
$ sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys [YOUR_PUBKEY]
Source : https://linuxconfig.org/ubuntu-20-04-gpg-error-the-following-signatures-couldn-t-be-verified | Last Update : Sat, 23 Apr 22