It is exactly by a stretch
Why not? Look at Figure 1 in the manual,
https://dlcdnets.asus.com/pub/ASUS/L...glish_1127.pdf the stand folds flat. The montior itself is 510.9 mm x 313.9 mm x 8.5 mm without the stand -- 20.12" x 12.36" very thin so it is totally within MLC limits and possibilities. This truly is peanuts, I have tried to squeeze a 13.5"x22" monitor in a carry on with questionable success
you sorta can in a shapeless rolltop, basically a tarpaulin sack with backpack straps but gosh that was a bad experience. You'd have no problems with a monitor this size for example in the Minaal or many similar bags.
It's this size, that nifty stand and USB C power which made this my dream. That it's 4K and OLED not so much -- I'd have lived with a full HD monitor at a reasonable (200 USD or so) price instead. No such thing.