How to expose paging data in REST export views
Enable pager Exposed option "Allow user to control the number of items displayed in this view" in rest display, then build custom module with views style plugin - to return results and pager data, and set in rest display

short code from custom style plugin:

$ret = $this-&gt;serializer-&gt;serialize(
 [
   'results' =&gt; $rows,
   'pager' =&gt; [
     'count' =&gt; $count,
     'pages' =&gt; $pages,
     'items_per_page' =&gt; $items_per_page,
     'current_page' =&gt; $current_page,
   ]
 ],
 $content_type
);


full code in gist: https://gist.github.com/svetlio/79f3c32667b21d89ed03cdb660308668

thanks to Dan's post here: https://www.mediacurrent.com/blog/8-insights-and-useful-snippets-d8-rest-module