This is what a realtor's own page looks like with our tour dropped in: one script tag, one custom element. The tour keeps running on our servers (tiles, password, analytics), but lives inside their listing.
<script src="https://HOST/platform/embed.js" async></script>
<nb-tour src="https://HOST/t/villa-turquoise/" ratio="16:9"></nb-tour>
<!-- CMS that strips custom tags (some WordPress editors): -->
<div data-nb-tour="https://HOST/t/villa-turquoise/" data-ratio="4:3"></div>
<!-- plain iframe, if nothing else works: -->
<iframe src="https://HOST/platform/viewer.html?tour=/t/villa-turquoise/tour.json"
allow="fullscreen; gyroscope; accelerometer" style="width:100%;aspect-ratio:16/9;border:0"></iframe>