Is your Backlight installation up to date? According to a post by @ben (PHP 8 and Wordpress - #8 by Ben), the is_admin error has been fixed a while ago. Check his link for a possible workaround.
Is your Backlight installation up to date? According to a post by @ben (PHP 8 and Wordpress - #8 by Ben), the is_admin error has been fixed a while ago. Check his link for a possible workaround.