Where is the man or manpage for a flatpak application?

How would I read the man page for calibre when it's installed from flatpak as below?

nicholas@gondor:~$ 
nicholas@gondor:~$ flatpak info com.calibre_ebook.calibre

calibre - The one stop solution to all your e-book needs

          ID: com.calibre_ebook.calibre
         Ref: app/com.calibre_ebook.calibre/x86_64/stable
        Arch: x86_64
      Branch: stable
     Version: 5.23.0
     License: GPL-3.0
      Origin: flathub
  Collection: org.flathub.Stable
Installation: system
   Installed: 360.9 MB
     Runtime: org.freedesktop.Platform/x86_64/20.08
         Sdk: org.freedesktop.Sdk/x86_64/20.08

      Commit: 13464e660f35716a725261af4b45d3abc199a3ce52ebdd9ee887c7ae623b5873
      Parent: 4f7f3b603f31cc781caf8260f887118a1bb466748891c9e122826728e25d3eed
     Subject: Update calibre-5.22.1-x86_64.txz to 5.23.0 (9184a3f3)
        Date: 2021-07-11 19:56:21 +0000
nicholas@gondor:~$ 
nicholas@gondor:~$ flatpak --version
Flatpak 1.8.2
nicholas@gondor:~$ 
nicholas@gondor:~$ man calibre
No manual entry for calibre
nicholas@gondor:~$ 

The search results I see are for how to use flatpak itself, which is only indirectly the question. No doubt the man pages are on the system itself.

calibre doesn't have man pages, if you've installed calibre v5.23.0 from their web page at https://calibre-ebook.com/download_linux. This is the recommended place to get the latest version of calibre.

Note: The flatpak version v5.23.0 from https://flathub.org/apps/details/com.calibre_ebook.calibre doesn't appear to have man pages either.

Note: At the https://calibre-ebook.com/download_linux web page, they indicate "Please do not use your distribution provided calibre package, as those are often buggy/outdated. Instead use the Binary install described below...".

If however, you've installed the older version of calibre v5.11.0 from the Ubuntu repos, or the Software app, it may in fact have man pages. Not recommended.

Start calibre. Click the HELP icon, or go to https://manual.calibre-ebook.com/ to view the calibre User Manual.