Starters cards stay visible on themes that hide empty elements
FixedSome storefront themes hide every empty element with a rule such as div:empty { display: none }, a common reset in Shopify themes. On those storefronts, a Starters card placed with the marker element or CSS selector mode could be missing from the page: the theme's rule treated the element we add as empty and hid it.
That rule no longer hides it. The card shows as it does on any other storefront. Inline buttons were never affected.
Your own control is unchanged. A rule you write on [data-iadvize-widget-host], display: none at a breakpoint included, still hides the card, and so does the hidden attribute. Cards you place with your own <iadvize-widget> element are not affected by this change.
Nothing to set up: the fix ships with the tag, so it reaches your storefront without a change to your snippet.