Hello x4you. I fixed the error in php8. You can find my answer in the forum. At the moment to fix this issue you must edit the file in your installation. The plugin editor from wordpress admin panel is usefull.
Edit the file inc > core > assets.php
Line 125
'error' => sprintf( __('%1$s. <a href="%3$s" target="_blank"><u>%2$s</u></a>'), __( 'Failed to load content.', 'shortcodes-ultimate' ), __( 'Open link', 'shortcodes-ultimate' ), '%url%' ),
Like this and the problem fixed. May be the creator will fix it soon. Cheers.