Ruby tags apply to other scripts as well like Japanese and Korean. See https://www.w3.org/TR/css-ruby-1/.

Sure but I saw it used for Chinese in the article. Very cool!

I use them whenever I have an excuse!

can they be applied to any text? might be useful if you have a hard to pronounce english word

Yes, <ruby> works with arbitrary text. There are quite a few styling options too:

https://www.w3.org/International/articles/ruby/styling.en.ht...

I’ve used them on Latin before.