I would say that if Manchester United's performance does not improve before the winter transfer window, United should first sack Erik ten Hag and hire a new coach. And then revamped their squad. In the previous transfer window, we saw that Ten Hag could not add the right players to the squad for Manchester United. He added young players like Hojlund to Skoda. And Hojlund is yet to score in the Premier League this season. And so I don't think Ten Hag will be able to select the right players for the squad in the next transfer window. He will waste money. While Chelsea's performance has gradually improved, Manchester United's performance is still very poor.
MU has actually had to fire Erik Ten Hag since the start of the season, but currently MU still does not have the option to find a suitable coach. The last rumor I read last year was that Zidane was considered the right figure, but Zidane has not yet responded to this rumor. Apart from Zidane, there is the name of the former MU coach, Solksjaer, who we all know has failed before. I don't know why until now MU has not tried to approach Conte, maybe with MU, Conte can give better results.
Erik ten Haag had good last season so board has quite some trust on ten Haag. Zidane is also a right figure but is he also up for the job? Last I heard that he said no to any offer he received last season. Zidane is a good candidate though. About Conte he also wanted some break from managing after Spurs sack so he was also out of the market. Possible that things have changed now so Conte could say yes. If I recall correctly, last to last season United were late on getting Conte and Spurs got Conte but this time United might want to rush things and sign Conte if he is in the market.