|Which is correct?
None of the software options _____ acceptable to the client.
This is an example of a rule that has changed to follow usage. Before the early eighties, the rule was that none stood for not one and always took a singular verb.
Now, however, the rule is that the verb form depends on the word that none refers to. In this case, none refers to options, which is plural, so we use the plural verb, are.