Euro-Office: sovereign in name only, or in reality too?

The announcement of the Euro-Office is welcome news. The coalition is credible, the governance is sound and the timing is perfect. Europe needs office software, and we are delighted to see such significant players allocating resources to make it happen.
However, we have a question. It is not meant to be hostile, but it is the only question that matters.

What is the native document format of Euro-Office?

https://blog.documentfoundation.org/blog/2026/04/01/euro-office/

@libreoffice

Regarding this argument:

OOXML is a format designed, controlled and managed solely by Microsoft

OOXML is registered as ISO/IEC 29500 since 2008, the same as ODF which is ISO/IEC 26300. I’m not supporter of Microsoft in any form and I’m aware of their lobbying going well beyond standardisation, but let’s stick to the facts.

@kravietz @libreoffice the facts are that they put money to get that approved as standard, the facts are that the 6000 (around that) pages of the implementation were not to be implemented, the facts are that they keep almost everything of their format out of their standard with propietary extensions in every release of MSOffice, the facts are that MSOffice does not use OOXML by default and you have to choose to save as it, and the document would break in most cases after exporting if you include images, tables and things and when you open it and save it again, it will override to the non-OOXML version with same extension.

Those are the facts too.