namespace should be lowercased in kubernetes. This is also true for the scenario where the namespace is generated from the project group-name.

app/models/project_services/kubernetes_service.rb

@@ -153,7 +153,17 @@ class KubernetesService < DeploymentService
   end
 
   def default_namespace
-    "#{project.path}-#{project.id}" if project.present?
+    return unless project
+
+    # 1. lowercase
+    # 2. replace non kubernetes characters with dash
+    # 3. trim dash from the beginning and end
+
+    slugified = "#{project.path}-#{project.id}"
+    slugified.downcase!
+    slugified.gsub!(/[^a-z0-9]/, '-')
+    slugified.gsub!(/^-+|-+$/, '')
+    slugified
   end
 
   def build_kubeclient!(api_path: 'api', api_version: 'v1')

changelogs/unreleased/mr-14642.yml

@@ -0,0 +1,6 @@
+---
+title: Auto Devops kubernetes default namespace is now correctly built out of gitlab
+  project group-name
+merge_request: 14642
+author: Mircea Danila Dumitrescu
+type: fixed