The 240LT fits without any modification in the 2 Slots GPU mode. It is the ONLY supported out-of-the box 240 AIO at the moment.With the thread search I wasn't able to find the discussion. The point is that the tubes should be shorter to fit properly. And why replace the liquid?
Maybe the EKWB AIO will be added to the list, but this is a decision by @Wahaha360 to have it official.
Of course, if you want to have better clearance, tubes routing, etc, you have to customised the LT240, so shortening the tubes (then replace the coolant) is the first move.
And this seems to be strongly suggested, because there are a lot of cases from user with the Eisbaer LT, reporting issue related to the plasticizer of the included tubes.
(There are a few pages back in this forum, maybe around page 200 or 220? Just go back and look for them!)