netflow
ntopng
needs
nProbe
(non free) to receive NetFlow
free
netflow2ng
exists
Akvorado
free (AGPL3)
high demands (ClickHouse time-series database)
ELK Stack
ElastiFlow
possible to obtain free Basic License:
no usage limits - commercial companies also
capacity limit - 4000 flow records per second
device limit - 25 devices for SNMP polling and trap