Preview of a page in an additional language fails if default and localized page is hidden
If you are logged in at the same time in backend, you can preview hidden pages (since ever).
But if you add a translation to a page (also a page record now in TYPO3 10), you also want to see this translated page before unhiding.
While the default page record has value pages.hidden=1 the translation has the value pages.hidden=0 it is not possible to use the preview for the translation. Without 403 handling the error comes up in frontend:
The page did not exist or was inaccessible. Reason: ID was not an accessible page
A quick fix is to also set the translation to hidden, so now you can view the translated page in frontend.
Playing around with the fallbackType in site configuration doesn't have any effect. Tested on a blank TYPO3 10.4.9
Updated by Alex Kellner 8 months ago
Update: While I could not reproduce it on a naked TYPO3-instance, we also face issues when parent or great-parent pages do not have any localization. This also prevents the preview in additional languages for $university with the same error message (in this case it don't matter if pages.hidden is set to 0 or 1 for the translated page itself). I just wrote this, because this could maybe help you and could be related to the described issue.