First step to move the site to Drupal 9

web/modules/custom/agaric_migration/agaric_migration.info.yml

@@ -2,7 +2,7 @@ name: Agaric Migration
 description: Migrate the content from the D7 version of the site.
 package: Custom
 type: module
-core: 8.x
+core_version_requirement: ^8 || ^9
 dependencies:
   - drupal:migrate
   - drupal:migrate_drupal

web/modules/custom/drutopia_case_study/drutopia_case_study.info.yml

@@ -1,7 +1,7 @@
 name: 'Drutopia Case Study'
 description: 'A Case Study highlights work done on a project.'
 type: module
-core: 8.x
+core_version_requirement: ^8 || ^9
 dependencies:
   - config_snapshot
   - drutopia_case_study

web/modules/custom/drutopia_creative_license/drutopia_creative_license.info.yml

@@ -1,7 +1,7 @@
 name: 'Creative License'
 type: module
-core: 8.x
 package: Drutopia
+core_version_requirement: ^8 || ^9
 dependencies:
   - config_actions
   - config_snapshot