For some reason the Eigen web page now has a menu in the upper-left corner that is blocking content. I can't find any way to make it go away, and it actively prevents people from looking up documentation on how to use Eigen. Can anyone help here? It fails with both Firefox and Chrome. Just go to http://eigen.tuxfamily.org/dox/.

Did anyone find a fix for this problem? I have the same difficulty

Quick Fix:
At the top of this menu is the word "Eigen". Do not click this text.
Click the upside-down triangle to the left of the text "Eigen". This will minimize the menu.

And I saw from user "irowe" on stack overflow
https://stackoverflow.com/a/62540482/13784831
that this is a bug and the Eigen team is aware of it, shown on their GitHub
https://gitlab.com/libeigen/eigen/-/issues/1918