Words can have different meanings in different contexts. Each industry has its own "jargon," in a way. Since you haven't provided a context, I can only answer in a general sense. So:
No, those words aren't opposites. "Actionable" means something you can do something with (e.g. information you can use as evidence in a lawsuit), and "substitute" means a replacement for an original (e.g. a substitute teacher for when the regular teacher is sick).
The opposite of "substitute" could be "original" or "regular."
The opposite of "actionable" could be "useless."
He did some actionable things in college which made the teacher angry. It is one word to represent adjective of a verb.
Sportsmanship is a word substitute for spirit of game
There is no one-word substitute in English for "son-in-law."
A word substitute for the sentence "A fault that can be forgiven" is "venial".
what word can I substitute for constitutes
you can not substitute me. The director Substituted lead actor.
what word is opposite of prudent
The word you want is florist.
The opposite of anything is it's absence. Silence would be the opposite of a word spoken.
which is the opposite to the word satisfaccion
There is no opposite to cobble.
This word does not have an opposite.