If the Mac was not at the “hello” screen, then the owner must relinquish their ownership. Otherwise, you will meet Activation Lock. Activation Lock is intended as a theft deterrent, and intentionally difficult to bypass. We can’t help bypass, and — absent sufficiently-convincing proof of ownership — Apple won’t help. That proof is usually an original purchase receipt from Apple or an Apple Authorized Reseller.
Here is what should be done by the owner: What to do before you sell, give away, trade in, or recycle your Mac - Apple Support
Here is what the owner must do to allow you to use it: How to remove Activation Lock - Apple Support
To erase, boot Recovery: Use macOS Recovery on a Mac with Apple silicon - Apple Support
And again, Recovery will not bypass Activation Lock.
You will need fast network for an erase and install, so maybe a library or Apple Store or restaurant or coffee shop or such. If you can simply reset it (after the owner relinquishes their hold) then you won’t need a fast network. Apple macOS activation does require network access.
If the seller has disappeared, you very likely got scammed, and now have a brick.
PS: Your AI lied. AI are terrible reference sources. They’re literally statistics guessing the next word, not a reliable reference source. They’re a chain of text autocomplete. Not “intelligence”. Even better, the increasing use of AI now means we get to answer the question and also explain where this AI hallucinated and why AI is a poor reference source.
The AI-suggested password reset does nothing for Activation Lock, nor would I suggest installing something as old as macOS 13 (“Ventura”). I’d here expect to install either macOS 15 (“Sequoia”) or the current macOS 26 (“Tahoe”) here. Apple has just started using the year as the version number, like vehicles. The Recovery will very likely get you macOS 26.3, too; the current version.
