the first English club sides to have won the treble multiple times
Manchester United haven't won the treble (EPL, FA Cup and CL) multiple times, they have only won the treble once, and that was in 1998-1999 season. Manchester City are the second team English team to win the treble, thus only two English teams (City and Manchester United) have won the treble, and they've both done it only once.
Manchester United won only one Champions League trophy almost two decades ago but then they did not win any Champions League trophy in the long 24 years. Manchester United are no longer considered favorites for the Champions League trophy. The only means of achieving European excellence is the Champions League trophy. They haven't won a Champions League trophy in a long time but they have no problem with that, they are only lying with the Premier League trophy and other minor tournament titles. After the change of ownership, Man U fans started to dream about this team again. If the plan goes according to plan and some changes are made in important places, maybe two eras will end their wait.