Drupal - What is the command that replaces 'drush variable-set'?

Following some more research it seems the new command is:

• drush config-set <config-name> <key> (where the old format was drush variable-set <name> <value>). Alias: cset.

So I'm not totally sure that I have this right (so comment and/or another answer from someone who does would be great...), but it seems that the config that includes emails are: contact.form.feedback recipients, update.settings notification.emails and system.site mail.

This update is the result for some good discussion (below). Note that some settings are arrays (rather than strings):

www/drupal8# drush config-get update.settings notification
'update.settings:notification':
  emails:
    - [email protected]
  threshold: all

to update this you need to run:

drush -y config-set update.settings notification.emails.0 [email protected]

Source: Leverage Drush 7 for Drupal 8.

^{Note: Drush 7 no longer supports Drupal 8, but this still applies.}

Additional follow-up,

To find the identifiers for the config to get or set,

• You can NO LONGER guess at the machine names of variables just by inspecting system settings forms. There used to be a 1:1:1 match between the form element seen on many config screens, the $config['varname'] you could put into $settings.php, and drush vset/vget
• The config manager in the ui (found at admin/config/development/configuration/single ) provides something of a variable browser.

I wanted to update my local.settings.php to always disable css & js aggregation when downsyncing.

D7 :

$conf['preprocess_css'] = FALSE;
$conf['preprocess_js'] = FALSE;

D8 :

$config['system.performance']['css']['preprocess'] = 0;
$config['system.performance']['js']['preprocess'] = 0;

(And note that this type of override WILL NOT show up in your Admin UI, or in drush config-get ... though it will take effect)

This worked for me. It's a Drush PHP EVAL command.

drush ev '\Drupal::state()->set("MY_VARIABLE", "MY_VALUE")'

Here it's being used to set the state of MY_VARIABLE

You can also get the state of a variable:

drush ev 'echo \Drupal::state()->get("MY_VARIABLE")'