Do I need to buy my own ISBNs as a self-published author?

Do I need to buy my own ISBNs as a self-published author, or can I utilise the free ones provided by Amazon KDP, Lulu, Kobo, Ingram Spark, and other services instead? This question is an age-old dilemma, and I will provide satisfactory answers.

An International Standard Book Number (ISBN), for those of you unfamiliar with the acronym-heavy lingo used in the publishing industry, is the specific identification code given to books that are offered for sale. Retailers need ISBNs to help organise ...