Web Theme managers are working on scripting the bulk of the changes needed to get our Web Theme ready for D10. This will make the process much smoother (and easier) than past migrations. Below are the docs from Pantheon that outline the general scope of migration, which is helpful for non-Web Theme sites as well. Please check this space for step by step directions coming soon.
For sites that are large in size, have a custom child theme or uses custom modules that are separate than what is offered out of the box with the Drupal 9 Web Theme, we recommend running a site audit to check compatibility.
Identify potential issues during the migration. This is the best starting point.
Setup a multidev for the D9 site and enable the Upgrade Status module.
After enabling the module, click Report => Upgrade status and review the list of modules from D9 that are incompatible with D10, fix any issues, updates, or custom modules needing changes.
Note: we are fixing all the D10 modules from the previous Drupal 9 upstream to make them compatible and ready for D10. You only need to audit the child themes or custom modules for your site.
Custom modules do not need to be requested but they must be configured to be D10 ready. The Upgrade Status module is a great asset for this, as well as what needs to be changed. Any custom modules must be placed in the correct folder to avoid being overridden: /web/modules/custom/my-site-name/my-custom-module
We are migrating all the contrib modules and Bootstrap base themes (ucsbweb and ucsbwesub) from the Drupal 9 upstream to the Drupal 10 upstream, except for modules that are not approved by Drupal Security or are still in alpha or beta versions. If no extra contrib modules were added at the site level, you don’t need to migrate anything. If we have any concerns about carrying a module over to D10, we will reach out to sites directly.
Note: The workflow process for D9 and D10 does not allows you to install modules at the site level while using the UCSB Web Theme. If you do this, it will be overridden upon the next site update.