Open Source Network Detection Software

One of my customers runs his company only with open source solutions.

Now he wants to monitor and secure his network consisting of FS switches (https://www.fs.com/). This from the endpoint to the server and also the complete network, so that a data outflow can be prevented because it is detected as an anomaly.

For this purpose, I have worked quite conventionally with Vectra AI or Cisco Stealthwatch.
Is there an Open Source solution that reliably does the same as the two commercial solutions?

Thanks for the help