MySQL 8 is not yet supported: SQLSTATE[42000]: Syntax error or access violation: 1231 Variable 'sql_mode' can't be set to the value of 'NO_AUTO_CREATE_USER'.

Support for MySQL 8 isn't there yet. There's a small patch on that other issue you could try. But for the best possible experience, use MySQL 5.7 unless you are comfortable experimenting.

I have the same problem when using MySQL Ver 8.0.13.
Who can support this?

see #2966523: MySQL 8 Support

Any news about the conflict with MySQL 8?

Conflict should be resolved:

    452     // NO_AUTO_CREATE_USER is removed in MySQL 8.0.11
    453     // https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-11.html#mysqld-8-0-11-deprecation-removal
    454     $version_server = $pdo->getAttribute(\PDO::ATTR_SERVER_VERSION);
    455     if (version_compare($version_server, '8.0.11', '<')) {
    456       $sql_mode .= ',NO_AUTO_CREATE_USER';
    457     }

The issue should be actually solved for Drupal 8 according to #8.

Google returns this page as a first result even for Drupal 7 searches though so - in that case - you could use the following workaround:
1. Go to your settings.php file.
2. Go to your database settings array.
3. Make sure its init_commands matches the following:

$databases = array (
  'default' => array (
    'default' =>  array (
      'database' => '',
      'username' => '',
      'password' => '',
      'host' => 'localhost',
      'port' => '3306',
      'driver' => 'mysql',
      'prefix' => '',
      'init_commands' => array(
        'sql_mode' => "SET sql_mode = 'REAL_AS_FLOAT,PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO'",
      )
    ),
  ),
);

The sql_mode directive above contains all the values set by Drupal 7 but NO_AUTO_CREATE_USER.

@vensires
Thank you it's working for me.

For Drupal 7 see #2978575: Mysql 8 Support on Drupal 7
It is still WIP, patch #24 should get you started. Consider D8 solution better regarding sql_mode. Recommend changing the code rather than overriding with settings.php

@lakshmi_a Yes, just confirmed that solution from @venisires worked on my local instance too! (MySQL 8.0.19 - Homebrew, Apache/2.4.41(Unix), PHP/7.3.11)

Thank you @venisires!!a

This is working on Ubuntu 20.04 where default MySQL 8.0.20 & PHP 7.4
thank you

#9 working perfectly.

@vensires #10 perfect solution for me. Lifesaving.

Reverting the previous (I suppose accidental) version change since according to #2966523: MySQL 8 Support this issue is fixed in Drupal 8.6+.

Also set #2978575: Mysql 8 Support on Drupal 7 as a related issue to allow users coming here from search results to use the patch proposed there, hoping it will land to Drupal 7.x.

#9 is the perfect solution.

No, #9 is not the perfect solution. This issue is already fixed, proper solution is implemented.

The workaround in #9 can be used in older versions that don't have a solution as it is not back ported.

This issue should probably have been closed as duplicate and for 8.6-dev as the solution is not provided here and fixed in 8.6.

#9 working perfectly for drupal 8.3

#9 did it! thanks!

Merci a versires, version drupal 7.59