You'll need to have the Helm repository added to your local environment:
helm repo add regiocloud https://regiocloud.github.io/helm-charts
helm repo update
Which should allow you to see the Hookshot chart in the repo:
helm search repo regiocloud
NAME CHART VERSION APP VERSION DESCRIPTION
regiocloud/alertmanager-matrix 1.0.0 v0.7.2 A bot to receive Prometheus Alertmanager webhoo...
regiocloud/calcom 0.5.1 v3.7.8 A Helm chart for calcom
regiocloud/hookshot 0.2.0 5.3.0 Deploy a Matrix Hookshot instance to Kubernetes
regiocloud/lemonldap-ng 0.1.0 2.16.2 A Helm chart for lemonLDAPng
regiocloud/shlink-backend 2.12.5 3.6.4 A PHP-based self-hosted URL shortener that can ...