{{ partial "header.html" . }}

<div class="header">
  <h1>{{ .Title }}</h1>
  <h2>{{ .Site.Params.subtitle }}</h2>
</div>

<div class="content">
  {{ range ( .Paginate (where .Data.Pages "Type" "post")).Pages }}
    {{ .Render "summary"}}
  {{ end }}

  {{ partial "pagination.html" . }}

</div>

{{ partial "footer.html" . }}

{{ partial "header.html" . }}

<div class="header">
  <h1>{{ .Title }}</h1>
  <h2>{{ .Site.Params.subtitle }}</h2>
</div>

<div class="content">
  {{ range ( .Paginate (where .Site.RegularPages "Type" "post")).Pages }}
    {{ .Render "summary"}}
  {{ end }}

  {{ partial "pagination.html" . }}

</div>

{{ partial "footer.html" . }}

Remove .Data.Pages in favor of .Site.RegularPages
Remove .Data.Pages in favor of .Site.RegularPages

Using only .Data.Pages will only show a link to the Post page in the home page. Using .Site.RegularPages returns the homepage to a normal showcase of existing posts. This change happened starting at Hugo >0.57.