I am connecting my laptop that running KDE and Arch Linux to mini-computer without GUI via direct Ethernet cable. Then by using "shared to other computer" method in Connection system setting in my laptop, I am sharing my laptop internet connection to that mini-computer. The connection is successful but I need to now the local IP of that mini-computer so I can ssh it from my laptop. How do I know the local IP of that mini-computer without operating it? This mini-computer will be stationed without human interface.

Have you tried using the most common default IP address: 192.168.1.1

You can find your computer's IP using the command line with just one command. At first, I just changed the IP address by reading about it at https://routeriplogin.com/how-to-change-your-ip-address-on-android/. Now press Win+R and call the "Run" system component. Enter "cmd" and press OK or Enter on your keyboard. Immediately start the command line of Windows. Enter "ipconfig /all" without quotes and hit Enter. After entering this command, all the information about the current connections will appear. This method allows you to determine the computer's address on the local network.