Contrary to the answer in the linked question, allow me to propose that Sneak Attack doesn’t have a damage type because there is no type specifically mentioned in the text.
Not all damage needs to be typed
See this answer on the damage type caused by blood loss, as well as some in-universe examples of untyped damage: the Stirge’s Blood drain, the Bearded Devil’s Glaive, and the Horned Devil’s Tail. Some types of damage in D&D is untyped and does not fit with the default types.
Sneak Attack only says you deal extra damage, without a type mentioned
The text for Sneak Attack says only this:
Beginning at 1st level, you know how to strike subtly and exploit a foe’s distraction. Once per turn, you can deal an extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll. The attack must use a finesse or a ranged weapon.
You can reason out that, just as the blood loss over time does not have a well-defined type of damage, you can argue that the extra SA damage comes from the exploitation of the target’s distractions and weak spots — which is itself not a kind of well-defined damage.
This tweet claims that all damage has a type, given by Jeremy Crawford himself. This clearly shows the intent behind damage types. However, his tweet is directly contradicted by the Monster Manual, a core rulebook, by showing instances of damage that do not have a damage type.
Note that these instances are not mistakes because they are not in the errata. We are left with the designer stating design intentions that is contradicted by a core rulebook. The core rulebook is more authoritative than a tweet — that’s why it’s a core rulebook.
Without JC’s statement about all damage having a type, the viewpoint that some damage does not have a type is stronger.
You don’t get to choose the damage type of Sneak Attack as it is an untyped damage on top of your normal weapon damage dice.