What was / is the list deal if you don't mind me asking? Thanks
No worries! Long story short, the "List" is the method some U2 fans have used since 2001-ish to start a GA lineup in the days leading up to the North American show. Someone will get to the venue and hold a notebook while singing up names in the order which people come by. There might be "check in" times associated with it, depending on how early any list was started (which is sometimes days in advance and is almost never advertised online on social media and such - people are just expected to know about it ahead of time and see someone holding a notebook, etc.).
Typically, security for the venues will usually go along with it, and these fans will line up a few hours before they're supposed to at the venue (with the people running the List taking off people that don't arrive at said time - or don't check in at the times beforehand), then the line will start to be treated like an "official" one.
It's caused some drama over the years, because while most bands usually just have fans that'll show up the day of the show at whatever time and stick it out, this process has sort of become convoluted and causes headaches for people who see it as unnecessary. It also is a source of frustration for fans who aren't aware of the system, as it's extremely unofficial, and just show up at the time the venue says people should start showing up for GA. And when those fans are sometimes allowed by the venue to be first because they followed the venue's rules, other fans will sometimes be outright hostile to them for not following "the rules" of List lineups. That's just a fraction of the stories or situations though, really!
The band hasn't done anything about it though, which usually is taken as them supporting the situation ultimately. So while it's a lot of drama, it's probably something you have to work with if you'd like to have a rail or front row spot at a U2 show. But as many on here point out, if you're not too worked up about that, you can usually show up at doors or an hour before and after and be right behind the List people anyway! And as dramatic as it can be, there are positive for it too, as you end up meeting a lot of hard core fans who sign up for the process anyway.