Why can’t turn off the Sublime 3 updates notification by adding “update_check”:false in user setting file?

Add this line in your host file.

127.0.0.1       www.sublimetext.com

for linux, host file is /etc/hosts
and for windows it is C:\Windows\System32\Drivers\etc\hosts

Update : If you want to open sublime website on your browser then make sure to undo these changes.