We do carry over a few traditions like giving christmas cards in full
summer with lots of pictures of snow, singing carols with words full
of wintry descriptions, decorations of non-native trees (or replicas
of them), and eating and drinking some foods and drinks more
appropriate to winter than the heat of summer.

Out of interest, does that you mean you escape the ridiculousness of how long our run up to Christmas is?  Commercially, Christmas seems to start immediately after Halloween.  We go on until 12th Night (Jan 6th). Two months+ !!

I recall visiting Brazil where it seemed more like Christmas 'started' on Christmas eve and finished on boxing day (Dec 26th).

I wonder if some planets in the Third Imperium do much more with Holiday than others.  Or less.  (Obviously very low pop worlds might not do much, but I'm thinking of larger populations).

tc