Upgrade 2.3.5 -> 2.4.8 fails (Helm error)

Hello,

i tried to upgrade Rancher from 2.3.5 to 2.4.8.
I also upgraded helm from 3.0.0 to 3.3.4.
I did all the steps mentioned in the documentation. I also had to reinstall cert-manager.
As the last step i entered the following command:
helm install rancher rancher-stable/rancher --namespace cattle-system --set hostname=nameofourhost

But i get the following error:
Error: rendered manifests contain a resource that already exists. Unable to continue with install: Issuer “rancher” in namespace “cattle-system” exists and cannot be imported into the current release: invalid ownership metadata; label validation error: missing key “app.kubernetes.io/managed-by”: must be set to “Helm”; annotation validation error: missing key “meta.helm.sh/release-name”: must be set to “rancher”; annotation validation error: missing key “meta.helm.sh/release-namespace”: must be set to “cattle-system”

I really dont understand what i did wrong. I also tried to send the command without setting the namespace but then rancher gets installed installed into the default project and not the system project. I dont think this is correct.

Has anyone an idea what i can do to upgrade successfully?

Thanks.
Regards,
Martin