AH01144: No protocol handler was valid for the URL /index.php (scheme ‘unix’). If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.

a2enmod proxy_fcgi
Considering dependency proxy for proxy_fcgi:
Module proxy already enabled
Enabling module proxy_fcgi.
To activate the new configuration, you need to run:
systemctl restart apache2