Preamble
I currently manage a wiki based on MediaWiki 1.35 with MediaWiki-extensions-LabeledSectionTransclusion installed.
In advance of a future migration of the wiki to next LTS version (1.39) I set a private test environment up using the current 1.39.0-rc.1 pre-release with matching LabeledSectionTransclusion version.
Issue
Before enabling LabeledSectionTransclusion <section> HTML tag was not interpreted, as expected. After installing and enabling the extension, all the markup included in <section> tag is completely ignored so nothing is shown to the users.
Actions taken
I checked that the wikitext actually contains the <section> tag and I verified that the exact code produces a completely different output in production 1.35 version in respect to test 1.39.0-rc.1 version.
I activated error display and logging, but apparently nothing wrong happens, no errors or warning are shown or logged.
Question
Is this behavior expected because the MW-1.39-release is not yet final, or is this an issue specific to my installation?
In the latter case, can you suggest further steps to troubleshoot this issue?