This Debian package of Prometheus does not include the modern React web UI, due to the complexity of packaging it without violating Debian policy.
Although the classic web UI was removed in Prometheus v2.34.0, it has been carried over to subsequent Debian packages for a limited time. Since the classic web UI is no longer maintained by upstream, and since it lacks the full set of features that the modern React UI offers, the classic UI will be removed in a future Debian package.
Alternatively, you can deploy the React web UI yourself with the assistance of the
/usr/share/prometheus/install-ui.sh helper script.
You can also still use the HTTP API (e.g., with tools such as promtool or
third-party applications such as Grafana), and the special handler endpoints: