Current WPT results:

/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy-multiple-queued-navigations.html
  FAIL Multiple queued lazy load navigations do not crash the page - assert_true: The iframe should be navigated to the resource provided by the latest `src` mutation expected true got false
@http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy-multiple-queued-navigations.html:40:16
@http://web-platform.test:8000/resources/testharness.js:2590:30
@http://web-platform.test:8000/resources/testharness.js:2665:37
onload@http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy-multiple-queued-navigations.html:51:29

/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html
  FAIL Below-viewport srcdoc iframes load lazily - assert_true: The window load event should have fired before the below-viewport srcdoc iframe's subresource loads expected true got false
@http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html:52:16
@http://web-platform.test:8000/resources/testharness.js:2590:30
@http://web-platform.test:8000/resources/testharness.js:2637:40
onload@about:srcdoc:2:55
  FAIL Below-viewport data: url iframes load lazily - assert_true: The window load event should have fired before the below-viewport data url iframe loads expected true got false
@http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html:65:16
@http://web-platform.test:8000/resources/testharness.js:2590:30
@http://web-platform.test:8000/resources/testharness.js:2665:37
onload@http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html:96:38
  FAIL Below-viewport blob url iframes load lazily - assert_true: The window load event should have fired before the below-viewport blob url iframe loads expected true got false
@http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html:72:16
@http://web-platform.test:8000/resources/testharness.js:2590:30
@http://web-platform.test:8000/resources/testharness.js:2665:37
onload@http://web-platform.test:8000/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html:100:38

The former of these is bug 243198, the latter of these I haven't actually filed (but I don't think needs to block shipping, especially while Chrome fails them: https://wpt.fyi/results/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html?label=master&label=experimental&aligned

Igalia, any insights into how ready this is to ship? I hear you were perhaps waiting for lazy loading on iFrames to become part of the official HTML spec — which has now happened. Does the implementation need to be updated to match the spec? Is this ready to ship?

Pull request: https://github.com/WebKit/WebKit/pull/2748

Committed 252848@main (461deb6c6dd7): <https://commits.webkit.org/252848@main>

Reviewed commits have been landed. Closing PR #2748 and removing active labels.

(In reply to Jen Simmons from comment #2)
> Igalia, any insights into how ready this is to ship? I hear you were perhaps
> waiting for lazy loading on iFrames to become part of the official HTML spec
> — which has now happened. Does the implementation need to be updated to
> match the spec? Is this ready to ship?

Yes, should be fine to ship.