Is there a standard environmental indicator for Drupal 8 projects?
A standard way to use different settings files per environment is through the use of sites folders.  Check out /sites/example.sites.php in your Drupal 8 codebase. It gives instructions.

Basically, you'll copy this file from example.sites.php to sites.php.  You don't need to edit it, (but you can if you want to do something unusual).

Then for each site (or environment), you'll have a separate settings.php file in a folder named after the site.

So you might have


/sites/example.com/settings.php 
/sites/qa.example.com/settings.php
/sites/dev.example.com/settings.php
/sites/example.local/settings.php


If you are using git, you might want to uncomment this 
/sites/example.local/settings.php

if (file_exists(__DIR__ . '/settings.local.php')) {
  include_once __DIR__ . '/settings.local.php';
}


and git exclude

/sites/example.local/settings.local.php

so that each developer can customize his settings.

If you run drush, you can run from the site specific folder on that environment or specify the --uri parameter.

Of course, you could just add conditional code in your /sites/default/settings.php

if ($_SERVER['SERVER_NAME'] == 'example.com') {
  $config['system.logging']['error_level'] = 'hide';
}


If you jut want to change one variable, and you know that on your production environment $_SERVER['SERVER_NAME'] is available and correct, then this is an option.