Thank you all for your helpful answers.
The system was indeed an open box, but the store was adamant that they cleaned it up and reset it to OOBE before putting it up for sale - I guess they did not do that very thoroughly.
I deleted the services and related drivers, creating restore points...
Setting up an Asus TUF Gaming A16 FA608UM, I was surprised to see in the Process Explorer a couple of active service processes from a competitor, Lenovo.
The parent of this Service is C:\Windows\System32\DriverStore\FileRepository\lenovofnandfunctionkeys.inf_amd64_{a whole bunch of random...