FE Language overlay differs from BE
Content element record translations that have no default language record or where the default language is hidden are not shown in FE when fetched by TS (page.10 < styles.content.get). Extbase show this records and so does the backend in page module. There is no combination of sys_language_mode / sys_language_overlay which accomplishs this.
The default TYPO3 language overlay behaves not like I would expect. As a default, a record should be shown if
- there is a translation for the requested record OR
- the record is marked as "all languages"
In 15 multilanguage projects I made with TYPO3 there was not one case or client where this should be different. In my opinion one single option would be enough, namely: Should the default translation of a record be used, if there is no translation for the requested language?
It is disappointing that such an essential feature seems still not to work consistently (BE, TS, EXT) in the coming LTS release without helping out with the great (but not trivial) "tesseract" extension set.