Minecraft wiki entry for Evoker, associated text: 1 Totem of Undying. The Looting enchantment does not increase this drop, and it is always dropped, no matter if another mob killed it or not.
0–1 Emerald if killed by the player, with an increase by 1 with each level of looting, 0-4 maximum.
1 Ominous banner ‌[JE only] or Illager banner ‌[BE only], if they spawn as a wave leader in raid or take an ominous banner on the ground.
10 exp. upon player kills or if killed by a tamed wolf/summoned iron golem.