Blank page when add a new post with PHP 8 and SiteOrigin Widgets Bundle

Hi, thanks for getting in touch.

Please, try the following two steps:

Try enabling WP_DEBUG_LOG. A debug.log file will be output to your /wp-content/ folder if any errors are caught:

Debugging in WordPress

Try establishing a working baseline. Temporarily deactivate all plugins except for the Widgets Bundle. Temporarily switch to a default theme like Twenty Nineteen. With only Twenty Nineteen and the Widgets Bundle activated, does the issue persist?

With template “Twenty Nineteen” all works fine.

Thanks for your support