It did answer the question. LibreOffice isn’t doing this in fact no Apps can do it in W10+
The link to a german Wiki page is unfortunate, but there doesn’t seem to be an English equivalant.
You MUST go to W10 Settings, and change the Default App
Apps > Default apps
Select a program, (e.g. Photoshop, or LibreOffice), and set defaults for each file type
For Specific File Extensions the A-Z list may be a better choice.
Apps > Default apps > Choose defaults by file type
Set this, and only Windows (Or the USER) can change it.
W10/W11 won’t even allow apps to change existing file default file associations, they can only set brand new ones.