For Grafana v9 it is enough to put
OHG_DEFAULTS["panelPath"] = "/d-solo/";
in openhab-grafana-user-defaults.js

For Grafana v9 it is enough to put
OHG_DEFAULTS["panelPath"] = "/d-solo/";
in openhab-grafana-user-defaults.js

I just tried to reproduce this: Upgraded from 7.5.16 to 9.2.3 and added the above line to openhab-grafana-user-defaults.js, but this still results in errors "Dashboard not found" and "Panel with id 18 not found".
So I'll have to downgrade again :-(

I've been using d-solo in the URLs too for some time now. But I haven't found time to update the documentation/screenshots for that change. 😉

You can use the changes of #32 in my branch. I just retested this after upgrading my Grafana to 9.2.6.

I just tried it out and it now works for me, but only after I changed the Webview URL from
Webview icon=none url="/static/grafana-time.html?dashboard=heizung&fromItem=Chart_Period&...
to
Webview icon=none url="/static/grafana-time.html?dashboard=Fp_OvCHMz/heizung&fromItem=Chart_Period&...
(The prefix before the dashboard name can be grabbed from Grafana and is different for every dashboard, no idea where it comes from, but it seems to be required for Grafana 9).

Thanks to your help, so I was able to upgrade Grafana from 7.5.16 to 9.2.6 now :-)

I think I read one day that nowadays unique IDs are generated. Perhaps it also depends on your upgrade path if they have been applied to existing dashboards.