Does something like a 1 to 2 Ethernet cable sort of device exists ? Searched earlier on Amazon but it's never clear what their product is used for
A switch is the answer.
Though, purley recreationally you can technically split a single ethernet line into two different computers. Though each computer would be limited to 100mbps. Here is a video of LTT talking about ethernet splitters and making one towards the end starting at 5:40 in this YT video