When striking a Villager with a channeling trident during a lightning storm, they will not convert into a Witch, yet the player will still receive the advancement.
On a similar note, Pigs do not convert into anything when struck by lightning either, though this may be a feature as Zombie Pigmen were removed.
Mooshrooms still do convert into Brown Mooshrooms when struck by lightning, though.
These effects remain consistent when using /summon to strike the mobs with lightning.