I agree with you. It will not be easy for Manchester United to beat Lyon. In their last 5 matches they have only lost to PSG in Ligue 1. The first leg will be played in France. I think Lyon will not let United get a win. Of course Lyon will try hard to get a win as the host in the first leg because it will give them an advantage in the second leg. On the other hand United have also performed well in the last few matches even though they often get a draw. I favor Lyon or a draw for that match. It is difficult for United to get a win with their performance. Maybe they will get a win in the second leg when they play at Old Trafford.
Manchester United must work hard in the first leg and maybe they will not be so ambitious to implement the target of winning because Lyon has the advantage of playing at home. IF Manchester United is able to hold Lyon to a draw at home then when playing at Old Trafford it will be much more likely for Amorim's team to beat them. I consider a draw more because I am quite sure Amorim will try to instruct his team to play carefully and will not apply a full attacking strategy.
If the strategy works during the second leg, Manchester United has a much better chance of putting pressure on Lyon. The defense needs to be improved so that Lyon cannot score and that must be a strategy that can be implemented well by Manchester United when visiting Lyon's headquarters.