I agree with you. I think we can agree that Athletic Bilbao are the first favorites to win the UEL after seeing their form in La Liga. I also put Lazio as the second favorite and United or Tottenham as the third favorite. Honestly I don't think Manchester United can win the UEL because they are inconsistent with their form. That means they might beat Athletic Bilbao or Tottenham but there is also a chance they could lose to a team like Rangers or even Bodø/Glimt. If I am going to play it safe I think Athletic Bilbao is the only choice here. They are the most consistent among the other teams. They are also ranked 4th in the league this season and the 3 teams above them are teams playing in the UCL.
Although Athletic Bilbao is ranked 4th this season in their own domestic league, it does not mean that it will immediately be a guarantee for Athletic Bilbao to be able to win the Europa League. Because if you have followed this competition for a long time, of course you have seen how Sevilla got the Europa League trophy even though in their domestic league the team was not in a very good position in the standings. So this is not actually a guarantee that Athletic Bilbao will not lose in the remaining rounds of the Europa League this season because every team will definitely improve their performance during a break like now and when they are in a more crucial round.