The third-party TrueCharts apps catalogue has been deprecated.
Your options are:
Either look into how TrueCharts plan to offer migration for their apps to a solution they support. Maybe it’s been published already, I don’t follow their activity.
Run your apps with Docker in a jail using Jailmaker. This is a temporary solution, since the creator of Jailmaker, Jip-Hop, will step back from development of Jailmaker when the next version of TrueNAS is released.
Hold off for month-ish for the next version of TrueNAS SCALE 24.10 which will support Docker. This is the option I recommend if you can stomach the wait.
Everything @neofusion said is correct. I’d add to that that TrueCharts have their own support channels, and this isn’t one of them–though SCALE is most definitely an unsupported platform at this point.
But with all of that said, the error you’re getting seems to suggest that the Kubernetes service isn’t running. If you’re running Dragonfish, is the apps service running? If you’re running Electric Eel, it’s been removed. Or if you aren’t running this on SCALE at all (which I’m starting to suspect–I don’t think I’ve heard of anyone installing their charts at the CLI using the helm command), you’re in completely the wrong place.
So is the apps service running? And where did you get the idea to run helm install on a TrueNAS system? I know none of TrueCharts’ docs told you to do that.