Update errors - LinuxCNC NO_PUBKEY

[n_spect_r]

===========================
Install Updates Error log
===========================
Install Updates could not fetch the package cache information lists.
Go to https://www.linuxliteos.com/forums/ and paste the log below into the Software - Support - Updates section for assistance.

============ Log ===========

Hit:1 http://archive.ubuntu.com/ubuntu jammy InRelease
Hit:2 https://dl.winehq.org/wine-builds/ubuntu focal InRelease
Hit:3 https://brave-browser-apt-release.s3.brave.com stable InRelease
Hit:4 https://deb.opera.com/opera-stable stable InRelease
Get:5 http://linuxcnc.org precise InRelease [60.1 kB]
Err:5 http://linuxcnc.org precise InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3CB9FD148F374FEF
Get:6 http://linuxcnc.org buster InRelease [54.9 kB]
Err:6 http://linuxcnc.org buster InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3CB9FD148F374FEF
Reading package lists...
W: GPG error: http://linuxcnc.org precise InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3CB9FD148F374FEF
E: The repository 'http://linuxcnc.org precise InRelease' is not signed.
W: GPG error: http://linuxcnc.org buster InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3CB9FD148F374FEF
E: The repository 'http://linuxcnc.org buster InRelease' is not signed.