Some items needed for guild crafting/knowledge gain cannot be obtained at the moment:

Grotesque Flag Ornament from Imp Flags (https://bdolytics.com/en/EU/db/item/3021)

and

Statue of Blind Faith Ornament from Cultist Stone statues (https://bdolytics.com/en/EU/db/item/3020)
I have been grinding both for hours, and also other players reported, these mobs dont drop anything, and no one was able to obtain these furniture items, even with properly leveled characters (lvl 1-25 to get proper drops).
EDIT:
Also adding the Mutant Troll Statue https://bdolytics.com/en/EU/db/item/3052. According to community reports, they did not manage to drop it so far after quite a bit of grinding it. Please check the droprate for this also (and the evasion of the Mutant Troll boss, its ridculous).
Maybe it is an oversight, but in an old drop rework these items might have been turned off.

Either turn these drops back on, or allow to get the guild furniture knowledge from an NPC.