We'll create fresh WordPress site with Simple default timezone installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This plugin provides network administrators ability to set same time zone over all blogs in multisite installation in one click, and also it restricts changes of timezone from local blogs settings.
*Based on: https://premium.wpmudev.org/forums/topic/set-default-timezone-for-new-blogs-in-the-network
Only works with multisite installation!
Gutenberg: compatible!
The Simple default timezone plugin is supplied “as is” and all use is at your own risk.