Question Is this NVMe SSD safe to buy ?

https://aukro.cz/5x-samsung-pm981a-512gb-nvme-najeto-max-2-hodiny-7061152736

Basically for 500GB the price is phenomenal but my question is would this be fine to fit and work in a B550 motherboard with PCI-E 4.0?

I think it's an nvme that was pulled from a laptop, if you translate from Czech to English the seller explains.
Yes, it's made by Samsung for sale to laptop and ready made PC manufacturers and should work anywhere M.2 NVME slot is available. As it is PCIEx4v3.0 it will work at those speeds. According to seller it's practically new. It apparently had OS on it so I would suggest erasing everything and install OS after.