Thx. I have done so by reinstalling influx and grafana from the openhabian-config. Grafana and Influx work now again, data is stored and shown in Grafana. Strange enough, I had to execute influx -username YourUserNameHere -password YourPasswordHereagain to see the (now again correct) users and database settings. In a next step I will enable ZRAM again and see if it still works.
Out of that (for future installations) the right order is then:
- install openhabian
- disable zram
- install influx&grafana (from openhabian-config)
- do first configurations and check whether all works (functionally but also checking whether influx shows proper user and database settings)
- restart Raspi
- again check whether all still works
- enable zram
- again check whether all still works
Is that the proper order?