The Christmas Card from the Princely Family of Monaco is the only one I've seen so far that looks Festive and has a Christmas Tree.
Queen Sofia of Spain's Card has a traditional Nativity Scene.
The rest of the European Royal Houses have Family photos which are nice but not at all festive but this seems to be the trend.
The Christmas Card 2021 of the Swedish Crown Princess Family, sent to princess Birgitta and shown at the documentary of princess Birgitta today. https://i.postimg.cc/J1kDNGLV/B2-t.jpg