MRTG (Multi Router Traffic Grapher) is not described on any of the fetched sources, so none of the candidates can be confirmed as its replacement from the pages read. The closest fits by stated purpose are network and infrastructure monitors such as ntop 8 and Zeek 9, and general monitoring systems such as Prometheus 2 and Netdata 7. Only ntop and Zeek are clearly network-monitoring products; the rest cover broader observability or visualization.

A question back: Do you want a replacement for MRTG's router traffic graphing specifically (SNMP interface counters turned into graphs), or a broader monitoring stack?

1. 1

   ntopntop.orgwebsite read, tools not yet checked

   ntopng monitors network KPIs, hosts, applications and traffic flows in real time from a single console 8.

   WebsiteDocsGet started

2. 2

   Prometheusprometheus.ioverified and signed

   An open-source monitoring system with a dimensional time series database and a query language for alerting and dashboards 2.

   WebsiteDocs

   +47 community tools built for it

   for agents: monitoring · instrumentation · prometheus

3. 3

   Netdata Agentnetdata.cloudwebsite read, tools not yet checked

   Netdata is a flexible monitoring agent that can be used to monitor all kinds of infrastructure 7.

   WebsiteDocsPricingGet started

   +1 community tools built for it

4. 4

   Zeekzeek.orgwebsite read, tools not yet checked

   An open source, scriptable network monitor that provides deep insight into network traffic 9.

   WebsiteDocs

   +2 community tools built for it