Color calibration is the ‘proper’ way, in the current darktable - it does give all the control and more that traditional white balance does. But it can be a little disconcerting… Try using the eyedropper to select something white - maybe the wrapping paper perhaps? Then if the correction is too strong, (too blue) reduce the chroma slider to let some warmth back in.
Or, you can use the 4 ways tab in colour balance rgb to add a little warmth.
If you want to use the white balance module for adjustments, switch off color calibration, or set to bypass.
5 minutes later…
I used color calibration to white balance off the right-hand bit of wall, as that gave a very neutral-looking overall scene, then used colour balance rgb to add some warmth into both the midtones (power) and the highlights, and cool the shadows just slightly.
Faily standard sigmoid workflow otherwise - you can load my xmp if you like to see what’s there. 
PC170001.ORF.xmp (8.4 KB)
P.S. I’m sure that tree will look lovely at night with the room lights off, just lit by the fairy lights. Long exposure, small aperture maybe get some stars… 