The following signatures couldn’t be verified because the public key is not available while updating sudo apt update

I am trying to install some application on Ubuntu 20.04, for that I am trying to run command on terminal

$ sudo apt update

and I have got following error

Err:1 http://dl.google.com/linux/chrome/deb stable InRelease                                
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 78BD65473CB3BD13

Answer

I am got the same issue while running the below command

$ sudo apt update

In your case, you can follow below option to resolved these issue.

1. sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 78BD65473CB3BD13

   Or

2. sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 78BD65473CB3BD13

In first option, we don’t have to decide which port should be or you can go with second option. Either way, both will work.