Grafana installation error on Raspberry Pi 4 "Package grafana is not available"

I am trying to install grafana on Raspberry Pi 4 by referring to the link: Install Grafana on Raspberry Pi | Grafana Labs

I started executing the codes step by step. Seemed working but ran into trouble at one. It says: Package grafana not available when I ran the following code

sudo apt-get install -y grafana

screenshot of the installation:

what could be the problem?

use this keyrings folder:

sudo wget -q -O /usr/share/keyrings/grafana.key
echo "deb [signed-by=/usr/share/keyrings/grafana.key] stable main" | sudo tee -a /etc/apt/sources.list.d/grafana.list
sudo apt-get update
sudo apt-get install grafana