"Looks like this project is already opened"

everytime i try to open my project i get this message despite the project not being opened

Force quit all unity processes in task manager

If Unity is not running, delete Temp/UnityLockfile from your Unity Project directory

If you have windows you can open task manager using key shortcut: Ctrl + Shift + Escape - and kill unity editor process which wasn’t shown

But what if I want to open a second instance?