This is just a heads up for those who don’t know any better like I didn’t. For some reason this information is not readily available.
The ‘-update flag’ was removed on 2.9.4 of the Kali Linux version of Nuclei for some reason.
In order to update the app to 2.9.6 you have to do a ‘sudo apt remove nuclei’ then download the latest version from Project Discoveries GitHub and place it in ‘/usr/local/bin’.
This will fix the update issue and you should be able to ‘-update’ like normal.