Would the same apply with the mfe container ? I am not sure supplying the EDX_PLATFORM_REPOSITORY would be useful as it needs to user repositories from multiple MFEs.
What I wanted to do was much much simpler than I thought.
In fact we have a fork. I noticed that some of the translations were still using the HTML code for the quote (') character instead of the quote itself.
All I needed to do was adding custom translations to my mfes following the instruction here: