I’d probably clean their room with pack of bin bags! Bin bag it all and out in the garage. Until I see some movement, whilst stuff is clear in room they can hoover, polish, do windows, and then help around the house to earn a bag or two back, phone or other precious devices I would hold on to, if they need laptop or something to do homework then they can use it and it gets put away again, the phones when they go back will be restricted and timers will be set on all apps which I can do with Apple. My kids generally have timer on anyway just before bed but usually the threat of being able to lock up their phone without touching it or hiding the charging cables to watch its demise normally works.