To avoid any misunderstandings, I'm talking about stuff that you would find under
/Library/SystemExtensions/
Usually sitting in a folder with a cryptic folder named like AAHHV55HIWJF&VHDI9
and often containing an item like com.nordvpn.macOS.Shield.systemextension
.
This is not about the Finder extensions that you would normally find in the System Settings app.
It is actually in my case said NordVPN Shield system extensiont that I just couldn't remove even using sudo via the Terminal. Here's what to do (only works on Intel Macs, I don't know how to get into recovery mode on Apple Silicon Macs).