How to use Views Photos Grid module with custom minimal theme
Issue was missing JS includes.
The working set is:

  &lt;script type="application/json" data-drupal-selector="drupal-settings-json"&gt;{"path":{"baseUrl":"\/","scriptPath":null,"pathPrefix":"","currentPath":"screenshots","currentPathIsAdmin":false,"isFront":false,"currentLanguage":"en"},"pluralDelimiter":"\u0003","google_analytics":{"trackOutbound":true,"trackMailto":true,"trackDownload":true,"trackDownloadExtensions":"7z|aac|arc|arj|asf|asx|avi|bin|csv|doc(x|m)?|dot(x|m)?|exe|flv|gif|gz|gzip|hqx|jar|jpe?g|js|mp(2|3|4|e?g)|mov(ie)?|msi|msp|pdf|phps|png|ppt(x|m)?|pot(x|m)?|pps(x|m)?|ppam|sld(x|m)?|thmx|qtm?|ra(m|r)?|sea|sit|tar|tgz|torrent|txt|wav|wma|wmv|wpd|xls(x|m|b)?|xlt(x|m)|xlam|xml|z|zip"},"viewsPhotoGrid":{"gridPadding":"1"},"user":{"uid":0,"permissionsHash":"797a0805952a191ed3acd8cc0feee5a8b53895cab4446ce069563dbdd87139da"}}&lt;/script&gt;

  &lt;script src="/core/assets/vendor/domready/ready.min.js?v=1.0.8"&gt;&lt;/script&gt;
  &lt;script src="//code.jquery.com/jquery-3.3.1.min.js?v=3.2.1"&gt;&lt;/script&gt;
  &lt;script src="/core/misc/drupalSettingsLoader.js?v=8.6.3"&gt;&lt;/script&gt;
  &lt;script src="/core/misc/drupal.js?v=8.6.3"&gt;&lt;/script&gt;
  &lt;script src="/core/misc/drupal.init.js?v=8.6.3"&gt;&lt;/script&gt;
  &lt;script src="/modules/views_photo_grid/js/views-photo-grid.js"&gt;&lt;/script&gt;


It doesn't work without the first messy line with data-drupal-selector. I wish I knew was is this good for...