Bugzilla

N.B.: As requested in comment #11 of bug 1667588, I opened this bug.
Especially since that bug's follow-up comment suggests the error might stem from bug 1677808 and/or bug 1677812 as both machines's `services.settings.server` pref already points to https://thunderbird-settings.thunderbird.net/v1 correctly, yet the error (DuckDuckGo is missing from the listing) still persists.

Also raising severity to S2 according to its docs: _(Serious) Major functionality/product severely impaired and a satisfactory workaround does not exist_ which is definitely the case as even the `Add from file` workaround fails to succeed:
> Uncaught (in promise) TypeError: Services.search.addEngine is not a function
> This call happens in `chrome://messenger/content/preferences/general.js`, line 701:
> `let engine = await Services.search.addEngine(engineAdd, null, false);`