DigitalOcean: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 35696F43FC7DB4C2

While upgrading Ubuntu 20.04 on a Digital Ocean Droplet, I encountered following error:

#do-release-upgrade

Hit http://security.ubuntu.com/ubuntu focal-security InRelease
Err https://repos-droplet.digitalocean.com/apt/droplet-agent main InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 35696F43FC7DB4C2

Doing a Google search didn’t give any clear solution so I tried different methods and finally found a working solution. Applying this fix let me upgrade Ubuntu.

The Solution

Go ahead and Google search for this issue and see if you can find a fix. You can also try asking ChatGPT to find the fix.

If you can’t find a solution then ask me in the comment below.