htmz (via) Astonishingly clever browser platform hack by Lean Rada.
Add this to a page:
<iframe hidden name=htmz onload="setTimeout(() => document.querySelector( this.contentWindow.location.hash || null)?.replaceWith( ...this.contentDocument.body.childNodes ))"></iframe>
Then elsewhere add a link like this:
<a href="/flower.html#my-element" target=htmz>Flower</a>
Clicking that link will fetch content from /flower.html and replace the element with ID of my-element with that content.