Who is in doubt that the UCL will be won back-to-back by Real Madrid since Mbape decided to join the team? I know a lot of questions would be if I said that because he is part of the team. Or without him can Real Madrid win the title again? The truth is that every player in Real Madrid is a very quality player, the club rarely signs players who are not super qualified for the task. Winning the UCL last season reminds Real Madrid that they are the true world champions and that the UCL title was meant for them. Propelling the club to sign Mbape which will be a start for a new era in the history of football for the club and the team members.
Remember that, in as much as Real Madrid is trying to keep dominating the EUFA Champions League competition, other major participants in the competition such as Bayern Munich, Manchester City, PSG, Dortmund, Inter Milan, and Liverpool aren't happy with that Real Madrid has recently become the dominating team in this game, So they are trying to step up their games too.
Despite Real Madrid recently bringing in of Mbappe into the club, it still not gonna be an easy game for Real Madrid this season.
You are right, I believe other clubs already have the mindset that Real Madrid will be a top contender next season in the UEFA Champions League so in order to challenge them in the competition they are also making efforts to improve in their performance and to add more good players to their teams so that they can challenge Real Madrid next season.
The teams you mentioned are all Champions League teams don't be surprised to see another thing that is not among the teams that you mentioned here winning the Champions League next season, I know that the Champions League competition is mostly won by elite teams but last season we witnessed a team that is not in good form getting to the finals and almost winning it if not that they couldn't make good of their chances to score goals. Dortmund is the team that surprised us last season when they got to the finals, another different team that is not listed here may win the Champions League competition next season even though Real Madrid is seen as the favorite right now because of the squad in the team.