Helm: How to Override Value with Periods in Name

Use \ to escape the dots in the key. Quotation marks are required to prevent shell interpreting the \ character.

helm install --values helm/jenkins.yml stable/jenkins --set 'Master.Ingress.Annotations.certmanager\.k8s\.io/cluster-issuer=letsencrypt-staging'

Helm requires these characters to be escaped: . [ , =

Source: https://paul-boone.medium.com/helm-chart-install-advanced-usage-of-the-set-argument-3e214b69c87a

You need to enclose the key with quotations and then escape the dots

helm install --values helm/jenkins.yml stable/jenkins --set Master.Ingress.Annotations."certmanager\.k8s\.io/cluster-issuer"=letsencrypt-staging