My own opinion is that Hume's argument is indeed open to question. This is not to concede that Hume's conclusion is not correct. It is correct. Skepticism is correct. This in its turn is not to concede anything to relativism.
Absolute skepticism is correct.
Nor does skepticism, as I have delineated it, recommend universal suspension of judgment, unless it is joined to the ruinous doctrine that all rational opinion is justified opinion. The level-headed skeptic, the critical rationalist, does not doubt that there is truth to be had, but thinks that it may be had only by making a lucky guess. If you judge that there is life elsewhere in the galaxy, and I judge the opposite, then one of us has hit on a fragment of the truth. That there are no grounds for thinking that I speak the truth, or that you do, does not imply that neither of us does. Remorseless though the logic is, it is at this point that reasonable people dig their toes in.