I honestly don't know either, what I did to "crosspost" was actually just double posting. First posting to kbin.social own magazine /m/Ukraine and then I accessed beehaw.org's /c/news community through our kbin instance by going to https://kbin.social/m/news@beehaw.org and did another identical post there.
If anyone has an easier way, please let me know lol.
Also, I think a crosspost button of sorts should be useful in he future, or a button to show in which other communities a certain link was posted - that'd actually help spread word of certain communities and could be quite useful.
China is most definitely looking at how western countries (and not only) respond to Russia's full scale invasion of Ukraine and taking notes, preparing for the future.
It's one of the many reasons why a bad response to Russia's invasion could lead to a bigger conflict in the future, possibly a world-war scenario.