Error when attempting to create sync directory I'm installing Drupal 8 with using Composer. During the requirements verification phase I receive this error.

Requirements problem
Errors found
Configuration directory: sync
An automated attempt to create the directory ../config/sync failed, possibly due to a permissions problem. To proceed with the installation, either create the directory and modify its permissions manually or ensure that the installer has the permissions to create it automatically. For more information, see INSTALL.txt or the online handbook.

As I understand it, the full path to the sync directory should be project_root/web/sites/default/files/config/sync, but if I run chown myuser:www-data to the project_root directory, Drupal will literally place the folder as in the error message, project_root/config/sync in my case.
I've never installed Drupal 8 via Composer, but this appears wrong and I can't find any relevant information.
Nothing wrong with that.

It is recommend to have the config folder outside of the public web folder; Drupal just doesn't have that. To keep the installation simple for non-experienced users, it puts that folder in the files folder, which has to be writable anyway.

Just create that folder and give Drupal write permission to it; you'll be fine.