Kill an Armor Stand do not drop armor or the armor stand item
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I tried it in survival, creative and adventure mode and the result was the same.
Is the gamerule doEntityDrops
set to false?

no, i can drop things myself but the mobs do not drop items, all the mobs i check it and wasn't only the armor stands
Actually, is the gamerule doTileDrops
set to false?

i resolved it, it was the gamerule DoMobLoot so thank you
Are you in creative mode?