We flipped the pref on in bug 1517090 and then made it only for nightly/early beta in bug 1534736. This bug will depend upon the bugs that "block" bug 1517090 and will track the actual flipping of the pref for "non-early beta and later" :)

I filed bug 1540402 to track all existing bugs in LSNG.
This bug should be probably converted to track only bugs that are essential for 67 beta and release.

All the blocking bugs here should be triaged and eventually be removed if they are not essential for 67 beta and release.
Full list of bugs will be tracked in bug 1540402.

AIUI this is targeting 68 now.

https://hg.mozilla.org/mozilla-central/rev/e6ae4508ea7d

Comment on attachment 9070312 [details]
Bug 1539835 - Flip pref on for LSNG for (non-early) Beta and Release; r=asuth

Beta/Release Uplift Approval Request

• User impact if declined: LSNG doesn't ship in FF 68.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): LSNG has been continuesly enabled in Nightly since Mar 7th 2019 (3 months ago). It was also enabled in early 67 beta, then it was automatically disabled.
  It has been enabled in 68 beta and we think it's time to enable it in actual/late beta too.
  If new problems show up which can't be easily fixed in 68 beta, we can just disable LSNG with a simple pref flip.
• String changes made/needed: None

Comment on attachment 9070312 [details]
Bug 1539835 - Flip pref on for LSNG for (non-early) Beta and Release; r=asuth

keep lsng enabled in 68.0b9 without EARLY_BETA

https://hg.mozilla.org/releases/mozilla-beta/rev/504624a04c76