Peace in the Donbass is advantageous, as strange as it may sound, to China. Against the background of the US trade war for Beijing, the Eastern European market is becoming increasingly interesting, and Ukraine is one of the largest foreign trade areas. For example, for the Celestial Republic, imports to Ukraine reach 10% of the total.
That is why settling the military conflict in the Donbass for China means that, first, they will be able to increase the amount of imports, and secondly, will open new opportunities for transporting goods. Currently, imports from the east are by air, water (which is unprofitable because there is no direct connection, and in the case of peace in eastern Ukraine - transportation by Russian land corridors.
In this case, Europe will lose the amount of imports to Ukraine. Which is extremely unprofitable for her.
Recall that since 2016, China is among the TOP-5 trade partners of Ukraine.