The following commands can be used to configure Netflow v9 flow reporting on Ubiquiti routers.

First enable Netflow v9, then specify the collector IP and port, then set the Netflow version.

set system flow-accounting interface eth0
set system flow-accounting netflow server 192.168.88.196 port 9995
set system flow-accounting netflow version 9
commit
save

That's it!