Pagebreaks <!--nextpage-->not visible / supported in Gutenberg

[ghost]

Have an existing page with html content similar to this, pagebreaks are shown in old visual editor as dotted line with "- - - PAGE BREAK - - -" text:

Page 1 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
<!--nextpage-->
Page 2 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
<!--nextpage-->
Page 3 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
<!--nextpage-->
Page 4 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.

Open page with Gutenberg, page gets converted to a single paragraph block, pagebreaks are not shown in visual editor, but are still there and used in frontend.

<p>Page 1 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
<!--nextpage-->
Page 2 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
<!--nextpage-->
Page 3 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
<!--nextpage-->
Page 4 Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.</p>

Expected behaviour: Show pagebreaks or cut page in different blocks with types depending on content between <!--nextpage--> markers.

Possible reason: <!--nextpage--> not supported by Gutenberg (yet).

[karmatosed]

Right now that's not been added but it may be: #1328. Closing this issue in light of that.

[ghost]

This issue breaks existing content.

@karmatosed: Your referenced issue is closed. How does closing this one as well solve the problem in any way?