Jeff King [off-list ref] writes:

If the problem is a racy deadlock, there is a reasonable chance that
some jobs may simply be lucky. Even if things like packing refs help, I
suspect the problem may still be lurking. Maybe I'm just a pessimist,
though. ;)

I share the pessimism X-<.

We had some HTTP/2 stalls/deadlocks in the past, and they were dependent
on libcurl and apache (actually h2_mod) versions. IIRC some of the
non-TLS code paths for HTTP/2 were not well tested, which led to
8f2146dbf1 (t5559: make SSL/TLS the default, 2023-02-23). Of course
after that commit those cleartext code paths should not be a problem, so
that is probably not exactly the issue now.

But it might be worth checking the versions you're running locally
versus what's in the GitHub runner.

True.