Hi,
completely removing Flash from everywhere (tools, viewer, the actions systems, the embedding code and the viewer packaging, the build-system, documentation, templates, examples and so on) was bigger topic and to avoid too big changes at these parts within the releases, this was done for the next separate version path 1.21 (which is already in development for a longer time).
That means the version 1.20.* will be the last one with Flash support,
and then with version 1.21 all about Flash will be removed (internally this is already finished).
But it's today already fully fine to work without any Flash files, just set html5=only and remove all swf files (or ignore them). Technically the swf files are only related to Flash and are not used for HTML5.
Best regards,
Klaus