Extra mouse buttons on the side or also click on the wheel can be used for copy and paste or any other actions. To make extra buttons work as you need on Linux use next steps from ArchLinux wiki .
1. Install xbindkeys and xvkbd
xbindkeys allows to bind mouse buttons to any action like open terminal, open browser, copy to clipboard, paste.
xvkbd allows to send to system keyboard pressing like Ctrl + C, F5 and so on.
apt install xbindkeys xvkbd