quartz/layouts/_default/_markup/render-link.html

{{$trimmed := strings.TrimSuffix ".md" (.Destination | safeURL)}}
{{$trimmed = replace $trimmed "%20" "-" }}
{{$external := strings.HasPrefix $trimmed "http" }}
{{- if $external -}}
<a href="{{ $trimmed }}" rel="noopener">{{ .Text | safeHTML }}</a>
{{- else -}}
{{$fixedUrl := (cond (hasPrefix $trimmed "/") $trimmed (print "/" $trimmed)) | urlize}}
<a href="{{$fixedUrl}}" rel="noopener" class="internal-link" data-src="{{$fixedUrl}}">{{ .Text | safeHTML }}</a>
{{- end -}}