Thank you for your answer. After including ‘aarch64’ in the arch list, building the package went smoothly.
I followed your tuto to create the .conf files and loaded the ipt_NETFLOW module.
I got a warning: ‘ipt_NETFLOW: loading out-of-tree module taints kernel’, but no error.
I could not verify the content of the capture, because Arch Linux does not have a Logstash package. There is a Elasticsearch package, but I have still to look if it is the full stack (with Logstash) and find how to use it.
Anyway, I could verify with netcat that some data is sent to the port 2055 of my server:
netcat -u -l -p 2055 > netflow.capture