Image rendering plugin/service installation in Kubernetes environment

Is it enough to set GF_RENDERING_SERVER_URL and GF_RENDERING_CALLBACK_URL in the Grafana docker image for Grafana to recognize it should use the external renderer service?
I still get this:
lvl=warn msg=“Could not render image, no image renderer found/installed. For image rendering support please install the grafana-image-renderer plugin. Read more at Image rendering | Grafana Labs” logger=rendering

If I install grafana-image-renderer in my Grafana 7.3.6 it starts rendering the image but not sure whether it is done by independent rendering service or by plugin and strange thing is that it is only picking Grafana homepage image:

Kubernetes version: 1.5
Grafana version: 7.3.6

Image rendering service deployment YAML:
apiVersion: apps/v1
kind: Deployment
metadata:
name: grafanaimagerenderer
spec:
replicas: 1
selector:
matchLabels:
app: grafanaimagerenderer
template:
metadata:
labels:
app: grafanaimagerenderer
spec:
containers:
- name: grafanaimagerenderer
image: grafana/grafana-image-renderer:latest
ports:
- containerPort: 8081
env:
- name: RENDERING_MODE
value: “default”
- name: RENDERING_CLUSTERING_MODE
value: “default”
- name: RENDERING_CLUSTERING_MAX_CONCURRENCY
value: “5”
- name: RENDERING_DUMPIO
value: “true”
- name: RENDERING_ARGS
value: “–no-sandbox,–disable-setuid-sandbox,–disable-dev-shm-usage,–disable-accelerated-2d-canvas,–disable-gpu,–window-size=1280x758”

Service YAML:
apiVersion: v1
kind: Service
metadata:
name: grafanaimagerendererservice
spec:
ports:
- port: 8081
targetPort: 8081
selector:
app: grafanaimagerenderer

image