Related to template support in Section Translation, a case was identified in T304293#8031763 where the template card does not show the name of the source template:

This is something that happens in some (relatively rare) cases, where the source templates miss a template definition. In this specific case for example, although the source template has an "about" attribute and thus is recognized as a block template by our code, it doesn't hold any template definition (no "mw" data attribute) and the source template name is not available. This is the reason why it's not displayed in the screenshot.

This ticket proposes to support better these cases by either (a) extracting the correct template name, or (b) use a generic "Template" placeholder text when that is not possible.