So i was playing a game and I don't really know if this is considered a bug but it just might be, if you move Lux in anyway it should interrupt her ultimate, well if you use** Ziggs satchel** right when she ults she will jump, but the ult still goes through. I've been around since Season 2 and this is my first ever post on the website, I mean if anyone can just look in to this its a bit annoying.
[slayer-jinx-unamused]
Lux's ult is only interrupted by death.
It doesnt interrupt, no idea how you dont know this you must not play cc champs.
You can blitz hook into thresh hook into naut hook her from mid lane to the jungle and her ult will still fire from midlane while shes mid air on dragon pit.
Its kinda bleh honestly.
as people have already stated 
ulti can only be interrupted by death.
this is because it is a cast and not a channel, most casts have zero cast time or very short cast time
however there are some notably long cast times which makes them noticeable because they become immune to cc while in them
which include
rocket jump at .25 seconds (while on ground once she leaves ground she can be hit and interupted)
arcane shift at .25 seconds
spear at .25 second (after it was doubled from .125)
ulti at .5 second
ulti at 1 seconds
these are all "Casts" and because casts cannot be interrupted except by death, they will go through regardless of CC or displacement.
you can read more into them here
Lux's ult isnt a channel it just has a long cast animation lol
Lux's ult, similar to Ez's ult, is just a long cast time, not a channel. If you've played since season two, you should know that
Lux's ult can't be interrupted, except by death.
if you move Lux in anyway it should interrupt her ultimate
No, her ulti can only be interrupted by abilities that specifically interrupt channeling abilities, like Victors field.
