Ronaldo playing for Newcastle doesn't look possible to me, Newcastle might no be a 'poor' club, but the take over by the billionaires who bought the club is still relatively recent, and it is yet to have any impact on the team. It would be queer to see Ronaldo playing for a club like Newcastle, it would be a new low in his career and i don't think he will be interested in it. If Ronaldo is to stay in Europe, then it has to be a big club that's playing in the CL, if not it's better he leaves for Saudi Arabia knowing his time in the spotlight/elite football is over.
I always thought that Cristiano Ronaldo would not be allowed to play in the Champions League this season anymore because he already participated in a european club championship this year with Manchester United. I just searched that up though and i found out that he could still play Champions League for another club because he is only suspended to play Europa League this season and i doubt he wants to play there anymore anyway. I also think that he will choose a club where he can play Champions League over any offer from other clubs even if those other clubs are offering way more money. Nowadays CR7 is only playing to set new records or to improve the ones that he already reached.
The rules regarding players for the Champions League have indeed changed and are not like they were in the past. Because at this time, even if the player previously played in the Champions League for example in team A and then moved to team B which also played in the Champions League, then the player would still be able to play. What's more about Ronaldo, who previously only played in the European League, so if in the transfer market later Ronaldo plays in a team that plays in the Champions League then of course Ronaldo will be able to play directly in the Champions League.
So there is no longer a problem if Ronaldo wants to play in the Champions League again this season, but the problem is that not many big teams playing in the Champions League are currently interested in recruiting Ronaldo.
But about Newcastle I think Ronaldo deserves to play there, even though this season Newcastle is not playing in Europe but next season I am very sure Newcastle will play in Europe whether it's in the Europa League or in the Champions League.
Because it would be useless if, for example, Ronaldo joined Chelsea and played in the Champions League this season, but for next season Chelsea will not play in the Champions League because Chelsea failed to finish in the top four. So yes, playing at Newcastle for Ronaldo for now I think it's still the right choice, because Newcastle have developed very much so far.