Change ( Remove ) mayo theme from drupal 9

sudo vim /home/chiao/public_html/drupal9/web/sites/default/settings.php

Uncomment this line:

# $config['system.theme']['default'] = 'stark';

Namely,  $config['system.theme']['default'] = 'stark';

 

Go back to drupal site and change the default theme.

Then, comment the above line in settings.php