There is no reason to assume the answer will be the same for all people. If we assume a for-purpose ought (“ought…in order to”), then bridging the is-ought gap is trivial, as I showed briefly but completely here. That is consequentialism, and it can bridge the is-ought gap without breaking a sweat. As I understand, universal consequentialist results that are scientifically formalized and proven become the domain of praxeology.
Morality of the type that ignores consequences (in other words, purpose-free ought) is personal morality. I can decide in my own mind, “I won’t lie, even if it has good consequences, because I refuse to be that kind of person - End of discussion!” That is not logical, but it is fine because it’s a personal choice. But insofar as morality is not personal it’s nothing more than a persuasion tactic to get others to do what you want.
Such tactics may employ logical-sounding arguments, but unless those arguments are based on consequences they cannot carry any logical weight. People may agree with non-logical arguments for ethics and decide to adopt them, but that is simply persuasion. People may also agree with logic-based arguments that are illogical, but that is simply confusion.
Bottom line, we can only say that we have convinced someone to adopt an ethic on purely logical grounds if that ethic (and/or the reason for adopting it) is consequentialist.