Main page teaser with module paragraphs?
The “manage display” teaser configuration page did not show the number of paragraphs to be displayed in the teaser view since the "Display Suite" module was not installed. I missed the display suite module because it was not mentioned in the cited article about paragraphs. :-(

It is, however, easily possible to also generate reasonable teaser views without having the Display Suite module installed: Just configure a content type with 2 fields for the page content: The first serves as single teaser/introduction field and the second serves as vehicle to choose among multiple and per CSS differently formatted paragraphs for the following content. The first field I call “intro field” in the following.

For the intro field (to me) there seem to be certain restrictions: If one wants to use a flexible paragraph item for this purpose, it seems to be only possible to show or hide the element on the teaser or full content page, respectively. (Within this respect, text_with_summary appears to make no sense as element of a paragraph bundle).

On the other hand, one could also use an unwrapped text_with_summary field as the first part of an article. This enables the full teaser functionality where one can select from mere shortening or providing an alternative abstract. Most important the manage display page will now let you choose “summary or trimmed” as teaser.