As I understand, yEnc don't work with UTF-8.

It is not really binary-to-text though, it is more "binary to binary which can pass through common NNTP servers/clients as long as common encodings like latin1 are used" The last part is critical - yEnc is incompatible with more complex encodings like UTF-8, which is why it is completely useless today.
https://news.ycombinator.com/item?id=34680371