For not the first time that this question has been posted, there is no bypass for Activation Lock other than with the password to the Apple ID that established the activation lock, or by presenting the original purchase receipt and matching photo ID and the iPhone to the folks at Apple.
You apparently have what is effectively if not actually a lost or stolen iPhone, and there is intentionally no bypass for what is a theft-deterrent mechanism.
Return this to the seller for an unlock, or for a refund.
As the seller is quite possibly unavailable as is often the case in these questions, turn this into the local police.
What you’re asking here for would make it vastly easier to re-sell stolen goods, which would be expected to increase thefts, which would cause (more) problems for everybody with an iPad or iPhone. Again, activation lock is a theft-deterrent.
The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community