Install with k3sup:
k3sup app install cert-manager
Then edit and reapply:
/home/pi/.k3sup/bin/helm template cert-manager --name cert-manager --namespace cert-manager --output-dir /tmp/charts/cert-manager/rendered --values /tmp/charts/cert-manager/values.yaml --set image.repository=quay.io/jetstack/cert-manager-controller-arm --set webhook.image.repository=quay.io/jetstack/cert-manager-webhook-arm --set cainjector.image.repository=quay.io/jetstack/cert-manager-cainjector-arm