Hi, Thanks to all for the input! :) Just found a way to avoid generating pdfs and get a "good as possible" formatting of the pages...the screen of a smartphone is not a 4k monitor, hehehehe ;)
There two apps available on f-droid.org. Both are open source and you need not to create an account to download and install the apps. Easiest way to browse this "app store" is by downloading the droid-ify with a browser and install it. This is one of the f-droid clients. Then you need "FTP Sever (Free)" and "IWS" (which is a small and local webserver). Create a user name and password with the FTP server, start it and connect to your smartphone with ftp from the command line or with Putty. Upload the "doc" directory from the distribution to a folder of your liking on your phone. Stop the FTP Server (the is a notification, which can be user for that purpose. Start IWS and direct it to the directory of the "doc" folder, which contains the "index.html" file. The browser of IWS does not show files. The tap the "browser" button inside IWS and VOILA! :) There it is: The Nim doc in all its beauty formatted for the screen of your smartphone. Works on tablet also... :) Have fun! Cheers! Take1234