We already ship Noto CJK (although a slightly older version that doesn't exhibit some of the bugs in punctuation layout we encountered with current builds).
EDIT: Whee, went too fast.
We ship Noto *Sans* CJK ;o).
You're absolutely free to sideload Noto *Serif* CJK, just like any other font. It may or may not suffer from the punctuation issues we've seen with its Sans-serif brethren, though
.
If you're set on one of the C/J/K, you're probably better off with the Language specific one that matches your language.
Avoid the variable and the subsetted variants, as we won't deal with those as well.
(It's slightly clearer on the get noto website, although the recommendations are a bit old/biased).
EDITē: And I can't even *find* the get noto website anymore, lol. Closest thing to it appears to be
https://fonts.google.com/noto now?