Can one capture the ‘soul’ or ‘spirit’ of a dying Illithid / mind flayer with a ‘Ring of Mind Shielding’?

Do illithids or ‘mind flayers’ have a spirit &/or soul to be captured in a Ring of Mind Sheilding? This is related to a previous question regarding the mind flayer return to a (previous / humanoid) form.

It seems that the invading parasite slays the (humanoid) target during the ceremorphosis process. This transformed biology may even keep memories, similar to a metamorphasis with a caterpillar chrysalis. But is this newly-born abomination any kind of life-force that survives death?

What if a mind flayer dies whilst wearing a Ring of Mind Shielding? What is captured, if anything?

Relevant quote:

If you die while wearing the ring, your soul enters it, unless it already houses a soul. You can remain in the ring or depart for the afterlife.

The reason for this interest: answers to this question may relate to the capture and preservation of consciousness in general. This may also pertain to the ‘death’ and re-animation of: undead, sentient magic items, golems, simulacra – or even seeking to ascertain the difference between a dwarven or human soul vs. elven spirits.