reverted:
--- b/cefrl.info.yml
+++ a/cefrl.info.yml
@@ -2,7 +2,7 @@
 type: module
 description: Provides a field type to store a CEFRL language level.
 package: Field types
+core_version_requirement: ^9 || ^10
-core_version_requirement: ^10.1 || ^11
 configure: cefrl.settings
 dependencies:
   - drupal:field
reverted:
--- b/composer.json
+++ a/composer.json
@@ -17,6 +17,6 @@
   },
   "license": "GPL-2.0+",
   "require": {
+    "drupal/core": "^9 || ^10"
-    "drupal/core": "^10.1 || ^11"
   }
 }