[Framers] [FrameMaker 2019] Customizing responsive HTML5 output: best practices and good documentation?

[Yves Barbion]

Hi group

I'm looking for best practices and good documentation (or user groups) on
how to use and customize FrameMaker 2019 responsive HTML5 output, generated
from unstructured Fm files and from ditamaps. The FrameMaker "Help" does
not help me very much:

https://help.adobe.com/en_US/framemaker/2019/using/framemaker_help.pdf

Thanks

Yves