What package missing for Luci graphs?

Hi there,

Using Imagebuilder, installed luci-minimal package set and it works fine:
liblua lua libuci-lua libubus libubus-lua uhttpd rpcd luci-base luci-lib-ip luci-lib-nixio luci-theme-bootstrap luci-mod-admin-full luci-lib-jsonc luci-app-statistics

I also installed the following collectd related packages:
collectd collectd-mod-interface collectd-mod-load collectd-mod-memory collectd-mod-network collectd-mod-ping collectd-mod-rrdtool

However I am unable to view the graphs for ping or any other with or without login.
The file exists as listed here too: Luci Public Graphs

With the stock openwrt firmware for WNDR3700 I was using public graphs flawlessly without login for years.
I am wondering what dependency is missing now that this is not working at all.