Hi @rups
This seems to be the same issue which I faced, Please go through the below ticket, so that you will get some clarity.
However, from what I understand, we should not use the old grafana.ini file. After upgrading, we must use the latest grafana.ini file and add the appropriate configurations to the most recent grafana.ini file. Whenever you perform an upgrade, you must update the grafana.ini file instead of replacing it with an old grafana.ini file.