Earlier quoted context omitted.
No, it's in the browser. Turn off all data collection and the bug disappears. https://bugzilla.mozilla.org/show_bug.cgi?id=1749908#c10
lower in the linked thread: > Telemetry has nothing to do with this, it just happens to be one of the first services with H3 load balancer.
If telemetry really had "nothing to do with" the bug, then the fact that telemetry "just happens to be one of the first services with H3 load balancer" wouldn't trigger the bug.