If you check out the software Kris uses in that video on Linux you could try to use that and get the logs from that, run the tests he does there, look into the logs and find the issue and show it to the seller, or use it as reference to send it into a reputable repair shop
As the buyer, you have to presume you're being given the runaround so they don't have to refund your money/replace the unit if you've shown them the issue and they're still trying to deny a refund/replacement
If you purchased the card via a reputable service, such as eBay, they do cover things like this in their warranty, as it's most likely not described as non-functional (experienced similar with my attempts to purchase a 6900xt during the madness last year)
But if not, outside of sending it in to a reputable repair shop, there's likely little you can do unfortunately. Issues like this is the reason why I tend to discourage people from purchasing newish hardware second hand. So many issues near the end of warranties
14900k • Z790 Apex Encore • 4090 • 2x24Gb-8000 • 1200 Corsair Shift • 420mm Arctic II Push-Pull • Noctua • Fractal Torrent • Guilded.gg/justifiers
