Nicolas Jackson might have played as a striker for Chelsea but he is also capable of playing on the wing. If I remember correctly Jackson was playing as a winger in his former club before he moved to Chelsea and he was very effective in that role so he can also take on that role for Manchester United if he joins but the question is why are Manchester United trying to do away with Garnacho when he is a very talented player are they going forward are backwards?
Everything depends on the coach's assessment of his players, and each team has a different perspective, including the Manchester United coach, who didn't fit into his desired scenario. Although Garnacho's performance on other teams was considered excellent, every club wants players who can lift their team and comply with the coach's established rules. I think there are many things to consider in this regard.