If he is willing to accept a salary that is not too big then there is a possibility that a European team will sign him, but if he asks for a high fee it will certainly be quite difficult for a team in Europe to re-sign him. Several teams that will compete in the Club World Cup have a short-term interest in signing Ronaldo such as PSG and Real Madrid, but this is still just speculation because Al Nassr themselves are trying to approach him for a contract extension. One of the Brazilian teams has also been linked with Ronaldo but so far there is no clarity regarding his future next season.
Ronaldo never compromises on salary just because of this, no European clubs were able to secure his services before joining Saudi Pro League. Right now in Europe just Sporting CP can secure him if he wants to end his career at his boyhood club. Currently nothing is sure because Al Nassr is trying to keep him while Al Hilal was also interested but this chapter is also ended while heading for MLS is also on cards because he wants to play in Club World Cup which is possible in case of having any good club in MLS or contract with any Brazilian club which are also trying to bring him.
Few are talking about Real Madrid and PSG, these are not realistic news because this is not possible for them but no one can talk about anything because in soccer many things can happen which looks impossible in the beginning; few days left in Club World Cup hopefully updates will be available in next few days.