The update orphaning dashboard[1] shows that over 10% of users who are more than two version out-of-date have not reported a value for UPDATE_CHECK_CODE_NOTIFY in the past 17 days. We should investigate why this is the case. [1] https://telemetry.mozilla.org/update-orphaning/

After splitting out users who haven't run Firefox for at least 2 hours since being orphaned in bug 1284933, the number of users that didn't send any UPDATE_CHECK_CODE_NOTIFY pings dropped to 1-2% (from about 10% previously). This issue now ranks as number 8 instead of 3 of all possible states that orphaned users are in when orphaned. Although we should still investigate why this is the case, the priority has dramatically decreased.

similar question here, is this still an issue?

The update orphaning dashboard is now handled by mhowell. Forwarding n-i.

There's still quite a few of these, yes. As the dashboard itself points out, this is the expected state for builds that had our updater disabled at build time, but I'm not sure how common those builds are, or how many of them would have telemetry enabled.

Bug 1393601 added whether MOZ_UPDATER was enabled or not but the dashboard hasn't been updated for this yet.