The overall process to upgrade Acquia CMS 2.x to the latest Drupal 10 version involves:

• update the text format to use CKEditor 5,
• updating CKEditor to version 5,
• removing unnecessary modules,
• upgrading Drupal to the latest version of 10.x

Steps to upgrade¶

1. Switch from CKEditor 4 to CKEditor 5.

   1. Install the CKEditor 5 module with the following command:

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      ./vendor/bin/drush en ckeditor5

   2. Click Configuration > Content authoring > Text formats and editors.

      Alternatively, append /admin/config/content/formats to your application name.

   3. Update each text format, such as Filtered HTML and Full HTML, to use CKEditor 5.

      For more information, see Using the CKEditor5 text editor for the “Site Studio” text format.

   4. Uninstall any previous version of the CKEditor module.

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      ./vendor/bin/drush pmu ckeditor
      
      ./vendor/bin/drush cex

   5. Commit all changes, deploy them to your development environment, and run the following commands:

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      ./vendor/bin/drush cr
      
      ./vendor/bin/drush cim --yes
      
      ./vendor/bin/drush updb --yes

   6. Verify that the site in your development environment works as expected.
2. Upgrade your Drupal core version.

   1. Remove incompatible and insignificant modules.

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      composer remove drupal/upgrade_status
      
      Composer remove acquia/http-hmac-php

   2. Add the HAL module to the codebase because it is removed from Drupal core 10.

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      composer require 'drupal/hal:^2.0'  --no-update --no-install

   3. Add the latest version of core and contrib module.

      You can remove modules that are not used in the project. For example, Webform and Google Analytics.

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      composer require "drupal/core-composer-scaffold:^10" "drupal/core-recommended:^10" drupal/webform:^6 drupal/google_analytics:^4 drush/drush:^12 --no-update --no-install

   4. Install the latest Drupal core and its required dependencies with the following command:

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      composer update -W

   5. Perform post upgrade activities.

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      ./vendor/bin/drush cr
      ./vendor/bin/drush updb -y
      
      ./vendor/bin/drush cex
      ./vendor/bin/drush coh:import
      
      ./vendor/bin/drush coh:rebuild

   6. Commit all the changes, deploy them to your Acquia development site, and run the following commands:

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      ./vendor/bin/drush cr
      
      ./vendor/bin/drush cim --yes
      
      ./vendor/bin/drush updb --yes

   7. Verify that the site in your Acquia development site works as expected.