"helm install prometheus" fails

❯ helm install prometheus --create-namespace -n monitoring \
           prometheus-community/kube-prometheus-stack --values prom-values.yaml

fails (with Error: INSTALLATION FAILED: repo prometheus-community not found).

I understand that something similar to:

helm repo add prometheus-community https://prometheus-community.github.io/helm-charts

is needed, but this brings another issue:

Error: INSTALLATION FAILED: Unable to continue with install: could not get information about the resource PrometheusRule "prometheus-kube-prometheus-%!s(int=0)" in namespace "monitoring": invalid resource name "prometheus-kube-prometheus-%!s(int=0)": [may not contain '%']

What's the proper way to install Prometheus?