Crystal Apothecary should collect clusters with #c:clusters tag. This will impove mod compatibility, such as allow collecting Certus Crystals from Applied Energistics and other mods in the future.

It collects blocks from the tag spectrum:crystal_apothecary_harvestable, which is

{
  "values": [
    "#c:clusters",
    "#spectrum:crystallarieum_growable_clusters"
  ]
}

so this is already a thing. Anything in particular you are missing?

Thank you, the new 1.7.11 version works! But Apothecary name got replaced with a placeholder for some reason

Aaaaah, that is a quite outdated version you are running. In that case updating will do :>

This setup doesn't work, it doesn't collect certus quartz.
#spectrum:crystal_apothecary_harvestable doesn't seem to include #c:clusters

This is on Minecraft 1.19.2 with Spectrum 1.6.12-1.19.2-leisure_time