Chrome has removed HTTP/2 push from their browser almost 2 years ago.
https://chromestatus.com/feature/6302414934114304

Recently, we've started seeing some issues that are exclusively related to us supporting HTTP/2 push - See bug 1915830 for a list of such issues, as well as other known bugs in our implementation. It also caused an incident in bug 1909271 when we tried to ship Extensible Prioritization Scheme for HTTP/2.

In order to avoid future webcompat problems only affecting Firefox, I think we should disable HTTP/2 push.
This bug will track flipping the network.http.http2.allow-push pref to false, with a separate bug to remove the implementation in a few releases if the deprecation goes smoothly.

HTTP/2 Push was involved in several web-compat issues recently.
See bug 1915830 for known H2-push bugs.

As such it's best to turn off the feature and align with Chrome
in order to avoid future push bugs only affecting Firefox.

Backed out for causing xpcshell failure on test_dns_by_type_resolve.js

Backout link

Push with failures

Failure log

Backed out for causing xpcshell failures at test_trr.js.

Backout link: https://hg.mozilla.org/integration/autoland/rev/22e0ba48f910d3749db421eb3552277bc7dccc9b

Push where failures started: https://treeherder.mozilla.org/jobs?repo=autoland&selectedTaskRun=Zt3ZzK8aSCSxgBf9692Yiw.0&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=9df375df8b809ac5b938fd14b069b7463f5c9900

Failure log: https://treeherder.mozilla.org/logviewer?job_id=473585820&repo=autoland&lineNumber=4670

https://hg.mozilla.org/mozilla-central/rev/77ed711b4717

How practical is it to uplift this to help with the webcompat problems?

Given that we've had a minor regression, I'd rather it ride the trains.
Unless we also want to uplift bug 1915134 with it?

[Tracking Requested - why for this release]:
This pref is currently riding the trains. We want to let it go to release, and ideally we'd also uplift the patches to the next ESR (128.5).
The patches needing to be uplifted are attachment 9421807 [details], attachment 9421244 [details], attachment 9421245 [details]

The necko team's recommendation is that we let this ride the trains to release.

Did you want to nominate this for the Fx132 relnotes? Please go ahead and do so if yes.

Release Note Request (optional, but appreciated)
[Why is this notable]: HTTP/2 Push support was disabled.
[Affects Firefox for Android]: Yes
[Suggested wording]: We disabled HTTP/2 Push due to it causing webcompatibility issues. This feature is not currently supported by any other major browser.
[Links (documentation, blog post, etc)]:
Intent to unship: https://groups.google.com/a/mozilla.org/g/dev-platform/c/vU9hJg343U8/m/4cZsHz7TAQAJ

Added to the Fx132 relnotes.

MDN docs changes for this can be tracked in the following GitHub issue: https://github.com/mdn/content/issues/36116

:valentin next week is the final week before esr128.5 goes to build.
Is this ready for an esr128 uplift request?

HTTP/2 Push was involved in several web-compat issues recently.
See bug 1915830 for known H2-push bugs.

As such it's best to turn off the feature and align with Chrome
in order to avoid future push bugs only affecting Firefox.

Original Revision: https://phabricator.services.mozilla.com/D220699

I'll request uplift today.
Try push: https://treeherder.mozilla.org/jobs?repo=try&revision=a200bb38e09060c448ffd486a34b9b106f8dd514

HTTP/2 Push was involved in several web-compat issues recently.
See bug 1915830 for known H2-push bugs.

As such it's best to turn off the feature and align with Chrome
in order to avoid future push bugs only affecting Firefox.

Original Revision: https://phabricator.services.mozilla.com/D220699

I've requested uplift for all three patches.

:valentin, the request is missing an Uplift Request form.
You can add it by selecting the Change Uplift Request form action

Removing NI, I was just looking at this patch in isolation. I see it's part of a stack that includes an uplift form.