Does Prometheus 2 still use the unmaintained charting library "flot charts" ?
No commits since 2014. Unfortunately, because it's a great chart library (actually probably the best free one), only the reliance on JQuery isn't that fashionable.
Edit: oh, it was Grafana and Kibana that used Flot charts (at least when I tried it two years ago, maybe things have changed) quick Google (2014): https://github.com/grafana/grafana/issues/222