Very easy to do!
Do you want to DEACTIVATE your PRIMARY PS4, but it’s not by you? You can DEACTIVATE your PS4 100% all online by going to the playstation.com website and signing into your account. Many people don’t know this, but going to the website is very easy to do. Once you sign in, scroll down to other settings. Then click on deactivate all. This will deactivate your PS4 as primary on all platforms.
If you want to deactivate a single console instead of all the PS4s or other Sony consoles, you will have to do it with the device. So if you do not have the system, go to the website and deactivate all!