Ukraine

If China decides to act in concert with the West, then it gains nothing – China probably doesn’t care much what happens in Ukraine – and loses this new influence in Russia, which Beijing probably does very much want.

That's pretty much it. China is currently in a spot it very much wants to be, vast natural resources from Russia are theirs for pennies and global west is mildly annoyed that China doesn't give a shit on Europe, but not enough to cause any meaningful harm with trade bans or anything. And try to guess who supplies the microchips and other stuff for drones which Ukraine has, and I'd guess China supplies a ton of other countries too whose tech toys are going to Ukraine.

As long as this status doesn't change there's absolutely no incentive for China to have any active part in the war. The longer current situation stays the stronger hold they can get on Russia and gain more profits for their industry.