When using the legacy back-office, I have a page containing an eZFlow layout, this page is available in 3 languages EN, ES and FR.
This page contains a block available only in FR and EN, and the "main_language" of this block is FR.

In my non-legacy_mode siteaccess (./ezpublish/config/ezpublish.yml), I configured language priority as :

languages: [esl-ES, eng-GB, fre-FR]

Problem: the eZFlow block is displayed in eng-GB, as the 1st fallback language available, and not in FR, the block's "main_language".

Moreover, when looking at the code of TranslationHelper::getTranslatedField(), I read :
"By default, this method will return the field in current language if translation is present. If not, main language will be used."
but the code does not reference any ContentInfo::mainLanguageCode at all.