Help of libreoffice does not work after Ubuntu 20.04 dist-upgrade (object not accessible insufficient user rights)

This is a bug 1869561, it is not solved.

Temporarily you can use the help from web browser by opening /usr/share/libreoffice/help/index.html location.

Or use newer version of LibreOffice from the official PPA:

sudo add-apt-repository ppa:libreoffice/ppa
sudo apt-get install libreoffice

A known bug. See https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/1869561

According to that report a fix is in the pipeline. Meanwhile, to see help, open a browser and go to file:///usr/share/libreoffice/help/index.html

Only an idea, but... the terminal command sudo dpkg -l | grep libreoffice-help should show you the name of the package where libreoffice help is located. At my laptop, there are two packages called libreoffice-help-common and libreoffice-help-en-us.

And the command locate libreoffice-help-common will show you the locations of the files.