Here is a link to the UpdraftPlus clone of my site running PHP 7.4:
A blank page means that PHP is crashing, usually due to a function conflict introduced by a plugin or theme.
Try manually resetting your plugins (no Dashboard access required). If that resolves the issue, reactivate each one individually until you find the cause.
If that does not resolve the issue, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), navigate to /wp-content/themes/ and rename the directory of your currently active theme. Hopefully, this will force the default theme to activate and rule out a theme-specific issue (theme functions can interfere like plugins).
Thank you James! It was The All-In-One Event Calendar by Time.ly version 3.0.1 plugin that caused the issue. I really liked using that calendar, so maybe some other version of it plays well with 7.4. Also, would you have any idea why a clone of the site (including Time.ly) worked just fine on the UpdraftPlus clone/staging server?
You’re welcome!
I suspect the cloned site server is operating under a different PHP configuration or whole version.
The plugin’s developers will followup with you at https://projectdmc.org/support/topic/time-ly-3-0-1-and-php-7-4-break-wp-admin-my-site-sidebar-widgets/