Calf plugins path

Hi! I’ve installed Calf Plugins on my Linux Mint 18.2, but I can’t find the correct path to make Ardour recognize them.
I’ve found this path “/usr/lib/x86_64-linux-gnu/lv2/calf.lv2/”. It’s full of “.ttl” files, but putting this path into ardour doesn’t make any difference! Ardour doesn’t load calf plugins.

Use the lv2ls command to list LV2 plugins. If they are shown in the output, there is a different issue with your plugins. If they are not shown in the output, then there’s a problem with the packaging/install location. Ardour uses standard LV2 plugin hosting libraries to find/discover plugins. If lv2ls can find them, so can Ardour.

The output showed me all the Calf plugins that Ardour can’t see!
What should I do now?

Thanks you Paul!
I had to install the --lilv-utils-- to run the command lv2ls. Since I installed this package, Ardour started seeing all Calf plugins!