Version: 25.2.0.1 (X86_64) / LibreOffice Community
Build ID: 520(Build:1)
$ rpm -q libreoffice-common
libreoffice-common-25.2.1.1-1.x86_64
This is our build in the repos. We just want to let you know that we are looking at the issue. 
I got this error from the flatpak install which tells me that I am “missing help packages” in this flatpak.
Have you double checked to make sure the language pack help files are installed? I just verified that the help files are not installed by default. So, for example, if your language is “US English”, then you want to a dnf info libreoffice-help-en_US from the terminal and you should see something like this:
N.B. on this system the package is available to be installed.
I have the rpm version from the repo and the help file is encluded. I show that package is already installed.
Is this helpful?
Help content is available as an org.libreoffice.LibreOffice.Help extension. You probably need to install it manually. (And, at least for now, it contains help content for all localizations, so is rather large.)