We can beat them but I wouldn't use the Lyon game as a guide. The CL is practically their only motivation at the moment.
Not only a matter of motivation. PSG can beat 18 French teams with an odd central midfielder and struggle against any decent side like Lyon.
PSG lost against Lyon because the midfield was weak:
- no pure defensive midfield/destroyer: Thiago Motta retired
- no box-to-box: Rabiot blacklisted but he has generally been disappointing when needed so it's not a big deal
- a central midfielder Verratti injured and another one Paredes who didn't play in the last 8 weeks IIRC
In order to win the battle midfield, we have:
- a former #10 Draxler
- Di Maria: known for being inconsistent throughout a match
- Dani Alves: 35-year-old
Without Verratti, United wins easily the 1st leg. With him, I don't know what could happen because:
- some players are very inconsistent and PSG is not used to play against good teams.
- the tactical system has been fully modified following the injury of Neymar (4-3-3 before versus 4-4-2 now)
In all honesty, impossible for me to guess the outcome.