Steps to reproduce the issue

1. Create (or reuse) a component that has an admin page.
2. Make sure the manifest file is named manifest.xml instead of <extension_name>.xml. According to the documentation (read it here) the manifest file of a component can be named manifest.xml or <extension_name>.xml.
3. Create the zipfile for the component so it can be uploaded.
4. Install it in a fresh Joomla server version 4.1.2.
5. Try and access an admin page of your component.

Expected result

• The admin page of the component

Actual result

• You'll see an error page. Even though the component installed properl, the admin page will fail to work. You'll probably see an error like 'Class ... not found' or 'Layout default not found'.

System information (as much as possible)

• Clean install of the Joomla 4.1.2

Additional comments

The following line in the code expects the manifext to be called <extension_name>.xml and that you component declares it namespace tag in the manifest, otherwise it will not generate an entry in the namespace map and you'll end up wasting time.

@chmst Please don't treat this as a support request like last time. I think its a bug.