It took me some hours, but finally I managed to get grafana up and running in ssl mode embedded in an iframe card in HA, accessible externally without certificate errors.
BUT: To get to that point, I had to enable anonymous access in grafana to be able to see the graphs without logging in at first and I needed to port forward the grafana port to be able to access the graphs externally.
I don’t like this solution at all… Is there any other way to show the graphs in an iframe without allowing general anonymous access to the instance?
BTW: I also tried using the “direct link rendered image” approach with a generic ip camera entity in HA. But unfortunately, rendering PNGs in grafana seems to be very resource-hungry. Only one graph takes about 8 to 10 seconds on a RPi 2. Because of that delay, the ip camera throws a timeout in the log and doesn’t display the picture.
Apart from that, 8 to 10 secs at 100% cpu power every 30 seconds for every grafana graph in HA (even if not displayed) is much more a problem, than a solution… 