Have the same problem here, fresh Local install, fresh site install with nginx, MySQL 8.0.16 and PHP 7.4.1.
Downgrading to PHP 7.3.5 does the trick for me. I pasted below the error message I get opening Dashboard → Updates.
( ! ) Warning: An unexpected error occurred. Something may be wrong with WordPress.org or this server’s configuration. If you continue to have problems, please try the support forums. (WordPress could not establish a secure connection to WordPress.org. Please contact your server administrator.) in /home/itspain/Local Sites/ecbshop/app/public/wp-admin/includes/plugin-install.php on line 183