All clubs have their own history, not only Man United who has a good history in their achievements, but all clubs in the European continent, we know the problems experienced by Man United this season, maybe everyone will support them, but the Europa League is very different, anything can happen even with unexpected things, Real Sociedad is not a random team, not even a team that is underestimated even though Real Sociedad has just suffered a big defeat against Barcelona, of course with their defeat in the Domestic League Real Sociedad does not want to lose in the Europa League because this could be an opportunity for Real Sociedad to advance further than now.
If you continue to be proud of history without achieving success after that it will be a story that is not so interesting and this happened to Manchester United because for the past few seasons they have been a very weak team. In terms of quality, the two are not that different at this time and it may be difficult to predict who will win the match. But Manchester United will travel to Real Sociedad's home ground and the result of the first leg will be enough to determine the steps of both teams to qualify for the next round.
The defeat from Barcelona is not a reference because they did face a much stronger team, but look at how Manchester United performed in the Premier League and it does not at all show the quality of the team as a candidate for the title.