While there may be debate as to whether this was an appropriate use of deadly force.
What is the meaning of "as to"
You could have looked up "as to" in a dictionary. com/definition/as_to No, you can't use "if" instead of "whether". Incidentally, "as to" is best analysed as a compound preposition taking the interrogative clause (embedded question) whether this was an appropriate use of deadly force as its complement.
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You could have looked up "as to" in a dictionary.
I found it straight away here: https://www.lexico.com/definition/as_to
No, you can't use "if" instead of "whether".
Incidentally, "as to" is best analysed as a compound preposition taking the interrogative