The statistics "tab" in the web interface (Luci) used to show me nice graphs, but now that I upgraded (via the corresponding webpage, which I assume uses
sysupgrade) to 19.07 I see nothing there any more.
I can't remember having to do anything special to (re)activate the collectd/graphs last time I upgraded (from 17.01 to 18.06, IIRC), but just in case, I followed the instructions at https://openwrt.org/docs/guide-user/luci/luci_app_statistics, but to no avail. FWIW
ps auxw | grep collectd tells me there's no collectd running, even after
/etc/init.d/collectd start and
This is a BT HomeHub 5a