I found a legal solution for those who can't buy "Cherub Rock".
Guys from Russia, Belarus and other sanctioned countries. You can get it like a steam-gift from a friend from another country. Today i tested this method with a friend from Ukraine and this works great.
I think I got it. Thank you very much for your answer. dreamed of playing rocksmith for more than ten years. But when this dream came true, I face difficulties at every step because i'm a noob)
Guys! Only need a licensed DLC "The Smashing Pumpkins - Cherub Rock" for custom songs to work? Just I have no way to legally purchase this add-on due to political events.