I don't know why people are arguing about Ronaldo so much. We aren't linked with a winger at all. Darwin is the only real attacker we have links with. Our winger options next year are Sancho (good), Rashford (had an awful year), and Elanga (average and young anyway). Ronaldo has never been an actual #9. He's always been best as a wide forward.
To me, it's pretty clear. I think if we get Darwin, we'll start him centrally, and then have him and Ronaldo drift around and swap with each other, Darwin being the guy who gets in behind while Ronaldo does his thing just in front of the defensive line, having more space out wide but being very much a forward (just not on the shoulder of the defence). Rashford will probably rotate with Ronaldo to rest him in all the cups. Sancho and Bruno to be the creators/link players in the line between the deeper midfielders and the forwards. Essentially a lopsided 4231, where Ronaldo is more forward and Sancho is more a creator. Sancho and Ronaldo can both play on either wing too, just they'd play very differently of course.
Doesn't really seem like an issue to me. Defensively off the ball, Darwin's work rate would help cover for Ronaldo's lack of, while he also has the pace and strength that Ronaldo might not have anymore to be the threat in behind.