LCHF has a reputation for being as po-faced and limited as the traditional "healthy eating" guidelines set out by our Dear Leaders, but it really isn't. True, if you're attempting induction, Christmas is not the best time to do it. But once you're in maintenance, you're likely to be averaging around 100g net carbs a day, and the occasional blowout has no impact on either your flab (of which you now have very little, of course) or your appetite.
With that in mind, here's a couple of ideas for Christmas. I'll add more as they occur to me. These are not really everyday food, but on a per-serving basis they have a surprisingly modest carb count.
Proper trifle
British trifle is basically jelly, custard and cream, typically with some tinned fruit and trifle sponges thrown in. It only needs a few minor tweaks to bring the carb count down.
Shop-bought custard powder is made with cornflour and colouring, so first you need proper custard, made with cream and eggs. It's basically the same ingredients as for creme brulee, which is another acceptable indulgence for low-carbers. Notice the modest amount of added sugar:
deliaonline.com/recipes/col...
You can swap out half the sugar for artificial sweeteners if you wish, but IMO it's a bit pointless.
Now for some trifle sponges. Although low-carb variants do exist, made with almond flour, I prefer savoiardi. Their carb/sugar percentage is pretty high, but they're very light, so the absolute amount of sugar/starch per serving is not excessive:
aseasyasapplepie.com/savoia...
You can also use these for tiramisu, which in its traditional form is also more-or-less LCHF-compatible, being mostly mascarpone and eggs:
askchefdennis.com/the-best-...
Back to the trifle. Use ordinary sugar-free jelly. Add some fresh fruit (raspberries, strawberries, or whatever you prefer). A small spoonful of strawberry or raspberry jam helps offset the rather artificial flavour of sugar-free jelly. Put the savoiardi at the bottom of the dish (you might want to sprinkle some sweet sherry over them) and carefully pour over the jelly; it's best to let it cool slightly before doing this, otherwise the savoiardi tend to disintegrate and/or float to the top.
When the jelly is set, you can add a layer of custard and return to the fridge. Top with whipped cream; if you're making an alcoholic version, whisk in a dash of brandy, sherry, or liqueur at this point.
Top with almonds, a dusting of grated dark chocolate, and/or fresh fruit pieces.
Turkey roast
Hopefully you know how to roast a turkey and vegetables: make sure you do roast your veg, rather than boiling them, using a generous amount of butter, turkey fat (if there's enough), or duck fat. For example:
culinaryhill.com/rosemary-r...
If you think you don't like kale - a very traditional winter veg that's getting quite fashionable - try this:
skinnytaste.com/creamy-caul...
I have absolutely no idea why this recipe specifies fat-free milk (I suggest a dash of cream instead), but the rest is basically correct.
Go easy on the Yorkshires, potatoes, and parsnips and load up on less carby vegetables like cauliflower, and you're on target for a pretty low-carb meal.