Are there any? I've scoured the original House Liao sourcebook, the Handbook, and Sarna. No mention that I could find.
Thanks!
Post Xin Sheng, there was a resurgence in older Han celebrations and holidays (Handbook House Liao, p. 62). So the Lunar New Year is big, and there are canon references to Year of the Rat, Year of the Dog, etc.. I believe there are also references to the autumn Moon Festival being an important observance (during the Xin Sheng war, Capellans used the Moon Festival as the jumping off point for an insurgency campaign in the Tikonov Reaches).
So those two are canon. Based on the statement that "older Han celebrations/holidays" made a comeback, you could add the Lantern Festival, Tomb Sweeping Festival, Dragon Boat Festival, Night of Sevens Festival, Double Ninth Festival, and Winter Solstice Festival. But those would be speculative, rather than being specifically mentioned in canon.
Aside from that, most holidays appear to vary widely from planet to planet.