Hi maroner pierre,
I understand you’ve already tried several suggestions for pinning the About page to Start in Windows 11 25H2/26H2 without success, and eventually returned to the older build that works better for you.
At this point, since the previous troubleshooting and the methods you found online did not change the behavior, I would avoid making further system changes solely to force this particular shortcut.
If Pin to Start is not available or does not work for that Settings page, a practical alternative is to access it through Settings > System > About when needed. You can also press Win + R, enter ms-settings:about and press Enter to open the About page directly.
One important consideration is that using an older or unsupported Windows build long-term is generally not recommended, particularly for a computer connected to the Internet. Moving to a currently supported Windows release when practical will help ensure you continue receiving the appropriate security and servicing updates.
I hope this points you in the right direction.