Does the following sentence have an antecedent? If so, where?: Mark says jokes all the time, most of which no one finds funny.
Yes, the antecedent for the indefinite pronoun "most" is the noun "jokes".
The indefinite pronoun "most" takes the place of a noun for an unknown or unnamed quantity of something (Mark's jokes).
There is no antecedent for the indefinite pronoun "no one" which takes the place of a noun (or name) for any person who has heard Mark's jokes.