the following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32

This error occurs when trying to install or update a package in Ubuntu or Debian that requires an authentication key which is not present on your system. To resolve the issue, you can import the missing public key using the following command:

python
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3B4FE6ACC0B21F32

This will fetch and add the missing key to your system's trusted keys list. After that, you should be able to install or update the package without any further issues.