OT - what's needed is a cull of the defunct PIs that no one actually uses (some people install everything… just because they can) -- example, how many people actually use Entities Manager or Recoll Full Text Search.
The issue EM attempted (and largely failed) to address has been covered by enhancements to the core - Link and Notes for all Category columns and calibre:// URLs etc. And calibre's FTS does for Linux, MacOS and Windows what the RFTS plugin does/did for Linux only.
The only way to find out how many people actually use a plugin is to release a version with a bug, the devil is tempting me to do that with EM… afaik I am the only person who tried it in anger
BR