There is almost always a better team, and the better team will either easily win, or barely get a tie or a loss, but the better team won't get dominated, that is very rare. Or worst case, two teams will be close to each other, and either one of them will barely win or there will be a tie. With United, betting is impossible because you have literally zero clue what is going to happen with the game and you can't predict the result.
Unbeaten in the Europa League might be a consideration for betting but the consideration might be a draw. Both teams will fight harder in the first leg because maybe this is a chance they can get in the second leg. If one of them is able to take advantage of the first leg to get a win then the chances in the second leg will be quite potential to win the match again.
I rarely bet on Manchester United because this team is difficult to predict and it is too difficult to maintain the performance of the game especially in the Premier League, but if you look at Sevilla's history in the Europa League maybe Manchester United has almost the same.
Considering the first game is played at Lyon, could we maybe say that they would have the edge over United? I know at these levels playing at home or away doesn't really have a huge difference, but we could safely assume that we could see Lyon being as good as United, so any edge you can have over your opponent is a great one.
Lyon players will sleep at their homes, wake up, shower, and go to the stadium. Whereas, United players will end up traveling to another nation, another city basically, stay at the hotel, and go play at another stadium then theirs. Could that give Lyon an edge over United? If the gap between the two teams were a lot, like if Lyon were playing against Real Madrid, then yeah this wouldn't matter, but could it matter against United?