Wizards of the Coast are not releasing Unearthed Arcana or Sage Advice this month, as stated on Twitter.
Sadly, the gnomes made a strong case for time off this month. There will be no Unearthed Arcana or Sage Advice articles published this December. We'll be back with full <s>#</s>DnD technomancer support in January! <s>@</s>mikemearls<s>@</s>JeremyECrawford
The technomancer mention means nothing, by the way. They clarified that here.