linux – How to stop/disable grafana server starting on boot?

I have installed two instances of grafana on my local network. Now I want to disable one of them.
systemctl stop grafana-server just work until a reboot. How to completely stop the server from starting on boot?

Suddenly the internet is filled with tutorials how to start the server, but not real explanation how to completely stop it. I spent half an hour to find it. I will leave this question with an own answer because surely somebody will face this problem in the future.