I did have a quick play with Grafana Cloud using the default dashboards for their linux agent were so incredibly slow when trying to navigate simple metrics.
That has not been my experience whatsoever. At work we run our own self-hosted Grafana open-source and it's been fantastic. I've also run it on my own Raspberry Pi 4B at home and it's worked very well.
Yeah, that's not great. The interface seems snappier for me, but I may just be partial. I dunno. There is no perfect solution, but Grafana has been pretty amazing in my experiences.