This issue is a work in progress and the summary will be updated as needed.
This will presume a fresh 9.5 build vs a fresh 10.0 build, but will be expanded as needed to include notes about more specific scenarios.
Before you upgrade
Upgrade to the latest Sector 9.5.x and enable the "upgrade status" module. The report it gives you will be helpful to your particular situation. As far as Sector modules go, everything shipped from 9.5.8 will be completely Drupal 10 compatible.
You will need to remove and replace obsolete modules: especially all CKE4 and WYSIWYG modules. Enable the new sector_text_formats module to give your site new CKE5 profiles that will match what we're shipping with fresh Drupal 10 builds. Every text field will have to be manually switched over for now.
Modules you MUST uninstall before continuing:
* sector_wysiwyg_utils
* anchor_link
* fakeobjects
* wysiwyg_template
* wysiwyg_template_core
* upgrade_status
* better_normalizers
If you are using an older site, check that color, hal, and seven are all properly uninstalled.
When you upgrade
Check your project template to made sure it runs closely to the official project templates for Drupal 10 [LINK]. Some dependencies will need their version numbers increased (todo: specify which) and some 3rd party sections can be removed, like all CKE4 plugins in the "repository" section.
There is a bridge package we support that will keep Display Suite, Radix, and more:
https://www.drupal.org/project/sector_legacy →
If you are sub-theming from the Sector Radix Starter, include that as well:
https://www.drupal.org/project/sector_radix_starter →
Sector 10 tries to be completely theme-agnostic and does not come with a "base theme" any more. However, example themes that can be copied as a starting point will continue to be included. Existing sites should simply ignore this and keep what they have, but keep this in mind for any future projects.
Missing packages on upgrade
Here is a list of modules that are in Sector 9 and not in Sector 10 as per drush status. If you add the sector_legacy package to your project it will grab the latest Drupal 10 compatible versions of these. If you don't want to use Sector legacy, you will need to decide which items in this list you want to add to your project composer.json as you upgrade:
* antibot
* components
* current_page_crumb
* ds_switch_view_mode
* field_delimiter
* inline_entity_form
* view_unpublished
* webform
* webform_ui
* xmlsitemap_custom
* ds
* ds_extras
and themes:
* radix
* sector_radix_starter
Make it so!
Assuming you've had a good look at the above, you've made sure you custom modules, themes, and any additional contrib are completely Drupal 10 ready, then your path forward is simple. Your Sector 9 site now uses CKEditor5 and any cleanup has been completed.
Change Sector's version string to the latest 10.0.x release in your composer.json, run composer update -W, follow that up with ./vendor/bin/drush updb -y and you should be able to visit your completely functional D10 site when the commands finish. If you've found further problems, simply revert to your last stable state (you have been committing changes to your project and taking database backups, right?) and go through the above steps in a more refined way until everything works as it should.