give it a try

templates/full-pipeline.yml

@@ -23,9 +23,9 @@ spec:
       
     opentofu_version:
       default: '1.6.0'
-      # options:
-      #   - '1.6.0'
-      #   - '1.6.0-rc1'
+      _options:
+        - '1.6.0'
+        - '1.6.0-rc1'
       description: 'OpenTofu version that should be used.'
 
     # Images